Science Subtest II Flashcards
Non-Vascular Plants
They are limited in the height to which they can grow because their system of transporting water up the stem of the plant is less efficient than that of vascular plants. Ex. mosses and liverworts.
What is excretion?
It is the process of eliminating waste products of metabolism. It is an essential process in all forms of life. In single-celled organisms, waste products are discharged directly through the surface of the cell. In plants, waste is minimal and is eliminated primarily by diffusion to the outside environment. Animals have specific organs for excretion.
Organisms
- Organisms are individual living things that can carry out all basic life processes. Organisms take in materials, release energy from food, release wastes, grow, respond to the environment, and reproduce.
- Organisms may be made up of organ systems or may consist of a single cell, as in bacteria or protists.
- Examples include bacteria, amoebas, mushrooms, sunflowers, and humans.
What are simple machines? How many types of simple machines are commonly considered? Give examples.
A fundamental device for applying force. At one point, it was felt that all complex machines consist only of these simple machines in different combonations.
The lever, axle, pulley, inclined plane, wedge, and screw are the classic simple machines
Biological organisms are often classified into “levels” typically from smallest structural unit (cells) to the most complex.
- Cells
- Tissues
- Organs
- Organ Systems
- Organisms
Which of the following shows the relative positions of the sun, Earth, and moon during a solar eclipse?
A. This question requires the examinee to recognize the effects of the relative positions of the sun, Earth, and moon. A solar eclipse can only occur when the moon moves directly between the sun and Earth, casting its shadow over part of Earth.
What is the difference between a convex and concave lens?
The main difference between concave and convex lens is that a concave lens is thinner at the center than it is at the edges, whereas a convex lens is thicker at the center than it is at the edges.
A convex lens is a converging lens; it focuses the light passing through it to a point. A convex lens is used to bend light in a magnifying glass so objects appear larger than they really are. A concave lens spreads out light rays that have been refracted through it.
Milky Way Galaxy
It has a diameter of about 100,000 light years. There are about 100 billion stars in it. contains clouds of dust and gas called nebulae, planets, and asteroids. Stars, dust, and gas fan out from the center of the galaxy in long spiraling arms. All objects in the galaxy revolve around the galaxy’s center. The stars we see over our head every night are also members of the milky way family. Our sun is one of these stars and is located roughly 24,000 light years from the center of it.
Understand moon phases
The phases, or changes in appearance of the moon, depend on its position relative to the position of the sun. When the moon is between the sun and Earth, the side of the moon facing the Earth is dark. This is called a New Moon. As the moon travels eastward in its orbit, more of its sunlit side becomes visible to Earth and the moon is said to be waxing. As the moon orbits Earth, the side of the moon facing Earth eventually becomes fully lit. This is called a Full Moon phase. As the moon continues to around in its orbit, the lit portion of the moon visible to Earth becomes smaller, so the moon is now said to be waning. As it completes its revolution around Earth, the moon starts the cycle again as a New Moon
Label the parts of the animal cell.
States of Matter
Solid, Liquid, Gas
Don’t forget plasma! https://vimeo.com/5377756
What is electrical energy?
Electrical energy is produced by the movement of electrically-charged particles (electrons). The movement of electrons through a conductor, such as a wire, is called current (or circuit) electricity. Lightning is an example of a giant spark of static electricity, or the sudden movement of electrons from a cloud to another surface.
What is Commensalism?
In a commensal relationship, members of different species live together, and one member benefits without seriously affecting the other party. As a rule, the animal that benefits is usually the physically smaller of the two. The commensal organism may depend on its host for food, shelter, support, or transportation. The animal that benefits is known as the commensal, or symbiont, while the nonbenefitting species is known as the host. For example, some flatworms live attached to the gills of the horseshoe crab, obtaining bits of food from the horseshoe crab’s meals; the horseshoe crab is apparently unaffected.
Outer Planets
It consist of two gas giants—Jupiter and Saturn—and two ice giants—Uranus and Neptune. They often have dozens of satellites and rings composed of particles of ice and rock.
What is Newton’s First Law of Motion?
Newton’s First Law of Motion states that an object at rest will remain at rest and a body moving with a constant speed in a straight line will maintain its motion unless acted upon by an unbalanced external force. An example of force that opposes the motion of a body is friction.
Eons
the longest intervals of geologic time and are divided into smaller time intervals known as eras.
What are the differences between (domain) eukaryotes and (domain) prokaryotes?
Eukaryotes consist of all organisms with cells that have true nuclei and membrane-bound organelles. Four kingdoms—animals, plants, protists, and fungi—fit into this domain.
Prokaryotes have neither nuclei nor organelles with membranes. True bacteria fit in this domain.
Tissues
- Tissues are made up of cells that are similar in structure and function and which work together to perform a specific activity.
- Examples of specific tissues include blood, nerve, and bone.
- Humans have four basic types of tissues: connective, epithelial, muscle, and nerve.
What is a mixture?
A combination of two or more substances that are not chemically combined
Current Electricity
Current electricity comes from a stream of electrons moving through a conductor, such as copper. Some materials allow charges, usually electrons, to flow through the material. These materials are called conductors, and the flow of charge is called current.
Some materials are better conductors than others; they offer very little resistance to the flow of electrons. Most metals are very good conductors—copper, silver, gold, aluminum, or steel, for example.
However, not all substances are good conductors. Materials that do not conduct electricity well are called insulators. Rubber, plastic, wood, cloth, glass, and dry air are good insulators; they have very high resistance to the flow of electrons.
Big Bang Theory
12 to 14 billion years ago, the universe consisted of a small, extremely dense, and extremely hot point called a singularity. It expanded very rapidly from this hot, dense state into the vast and much cooler cosmos we currently inhabit.
Pacific Ring of Fire
It is an area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean; 90 percent of the world’s earthquakes and 81 percent of the world’s largest earthquakes occur along the Pacific Ring of Fire
Organ Systems
- Organ systems are groups of two or more organs that work together to perform a specific function for the organism.
- Examples include circulatory system, nervous system, and skeletal system.
- The human body has 11 organ systems—circulatory, digestive, endocrine, excretory, immune, integumentary, muscular, nervous, reproductive, respiratory, and skeletal.
law of superposition
oldest rocks are found on the bottom and newer rocks are found on the top; helps make a timeline
What is the formula 6 CO2 + 6 H2O → C6H12O6 + 6 O2?
This is the chemical formula for photoosynthesis.
6 Carbon dioxide + 6 Water + Light energy → Glucose + 6 Oxygen
What is amplitude?
A measure of the distance between a wave’s crest and trough
Tides
The regular changes in the elevation of the ocean surface. The cause of tides was not well understood until Sir Isaac Newton applied the law of universal gravitation to them. Newton showed that there is a mutually attractive force—gravity—between any two bodies, such as Earth and the moon. The pull of the moon’s gravity is greater at parts of Earth’s surface that are closer to the moon and less at more distant locations. Ocean tides result from differences in the gravitational attraction exerted upon different parts of Earth’s surface by the moon and, to a lesser extent, by the sunTo illustrate how tides are produced, consider Earth as a rotating sphere covered to a uniform depth with water. The gravitational pull is strongest on the side of Earth closest to the moon and weakest on the far side of Earth from the moon. This difference causes Earth to be stretched slightly. The shape of the solid Earth is not affected much by this difference in pull. However, because water is a fluid, it can easily flow from location to location in response to differences in the pull of the moon’s gravity. Because of the rotation of Earth, tides change four times a day—a high tide followed by a low tide and then the cycle is repeated. Water marks for high and low tides vary depending on the time of year and location.
Label the parts of a flower
The Sun
The closest star to Earth and the most closely studied. It is a medium-sized yellow star and is over 4 billion years old. It is made of extremely hot gas that is denser in the interior and less dense near the surface. The outermost layer, the corona, is composed of ionized gases that have speeds great enough to escape the gravitational pull of the
What is DNA?
deoxyribonucleic acid; contains the codes for protein, which are building blocks of life
There are 5 strategies for estimating (never use the phrase “guess” or “educated guess” with young students!). Name and define at least 2.
- Front-end strategy. The front-end strategy focuses on the left-most or highest place-value digits. For example, you can estimate the sum 67 + 91 by adding the highest place-value digits, 6 and 9. Thus, approximate 67 + 91 by 60 + 90 to obtain 150.
- Rounding strategy. Using the rounding strategy to estimate 67 + 91 would round 67 to 70 and would round 91 to 90 to yield 70 + 90 = 160 as an estimate for the sum.
- Clustering strategy. When operating with numbers that are clustered close to one another in value, group the operations to make the calculations easier. For example, to estimate the sum 594 + 603 + 622 + 586, notice that each of the 4 terms is approximately 600. So, the sum is approximately 4(600) = 2400.
- Compatible numbers strategy. Adjust the numbers so that they are easier to work with: in division, adjust the divisor, the dividend, or both, so that they are easier to compute. For example, to estimate 67 ÷ 3, observe that 67 is close to 66, which is divisible by 3. So, an estimate for 67 ÷ 3 is 66 ÷ 3 = 22.
- Special numbers strategy. Look for special numbers that are close to values that are easy to combine, such as one-half, or the powers of ten. For example, to estimate 51% of 89, observe that 51% is close to and that 89 is close to 90. So, 51% of 89 is approximately one-half of 90, or 45. This estimate is very close to the actual value of 45.39.
Geologic Time
Instead the time intervals are variable in length, using significant events to divide Earth’s history. For example, the boundary between the Permian and Triassic is marked by a global extinction in which a large percentage of Earth’s plant and animal species were eliminated.
What is heredity?
Heredity is defined as the transmission of characteristics carried by the genetic code from one generation to the next. Characteristics may be physical, physiological, or psychological as long as they are carried by the genes. Heredity explains why offspring look like their parents and why dogs always give birth to puppies and never guppies or butterflies. Through heredity, living things inherit traits from their parents.
Mitosis vs. Meiosis
The fundamental difference between mitosis and meiosis is that mitosis produces two daughter cells with the same number of chromosomes as the parent cell. Meiosis results in four daughter cells harboring only half of their parent’s chromosomes, which underwent recombination.
Mitosis is used by single-celled organisms to reproduce; it is also used for the organic growth of tissues, fibers, and membranes. Meiosis is found in sexual reproduction of organisms. The male and female sex cells (i.e., egg and sperm) are the end result of meiosis; they combine to create new, genetically different offspring.
Mitosis is asexual reproduction, where a single cell creates identical copies of the cell/organism. (There is mitosis in the process of sexual reproduction, but the cell it self is not combining and dividing)
What does this picture represent?
This is a factoring tree. It is one way that a student can perform the prime factorization of a number. In this instance, the number 1960 has been factored into the prime factorization 1960 = 2 × 2 × 2 × 5 × 7 × 7 = 2³ × 5¹ × 7².
What is Chemical Energy?
Energy stored in bonds of atoms and molecules is described as chemical energy. Gasoline and coal contain stored chemical energy.
Label the insect parts
What are the Life processes of Living Things?
Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition
When is an X-Y plot used?
X-Y plots are used to determine relationships between the two different things. The x-axis is used to measure one event (or variable) and the y-axis is used to measure the other. If both variables increase at the same time, they have a positive relationship. If one variable decreases while the other increases, they have a negative relationship. Sometimes the variables don’t follow any pattern and have no relationship.
Define Homeostasis
The ability to maintain a state of internal balance. For example, if the environmental temperature increases, the human body begins to perspire, and the cooling effect of evaporation decreases the surface temperature of the skin. Likewise, a disruption in any system will set off a diverse set of control mechanisms that return the organism to a state of internal balance.
What is incomplete metamorphosis?
About 12 percent of all insects go through incomplete metamorphosis. These include stinkbugs, earwigs, crickets, grasshoppers, cockroaches, ants, praying mantis, and dragonflies. Incomplete metamorphosis has only three life cycle stages: egg, nymph, and adult. The nymph looks similar to, but is a smaller version of, the adult. The nymph is also wingless. As nymphs grow, they shed their hard exoskeletons, a process called molting. There is no pupal stage during incomplete metamorphosis.
Static Electricity
Atoms normally have the same number of electrons as protons, the positive and negative charges cancel each other out and, as a result, atoms usually have no charge; they are neutral. Static electricity is the result of an imbalance between negative and positive charges in an object.
Normally, the protons and neutrons in the nucleus are held together very tightly. But some of the outer electrons are held very loosely; they can move from one atom to another. If an electron is removed from a neutral atom, the atom is left with more positive particles and acquires a positive charge.
If an electron is added to a neutral atom, the atom has more negative particles and acquires a negative charge. The more positive atoms or negative electrons you have, the stronger the attraction for the other.
For example, rubbing a shoe against a carpet creates an excess of electrons. When reaching and touching a doorknob a shock, or tiny spark, is felt or seen; excess electrons are released to recreate a balance of electrons and protons in atoms. Lightning is also a result of static electricity.
Water Cycle
What is heat energy?
Heat energy is created by the random movement of molecules from a warm substance to a cool substance. Temperature, measured in degrees, is an indication of the average kinetic energy of the moving molecules—the speed at which they move. If the molecules in a substance move slowly, the substance has a low temperature. If the molecules move rapidly, the substance has a high temperature. Heat energy is transferred in three ways.
Understanding the atom:
What is conduction?
Conduction is the process by which energy is transferred through matter by collisions between particles. It is the transfer of heat energy from atom to atom within a substance. As one molecule is heated, it begins to vibrate. As it does, it passes some of its energy to other molecules around it. Through this process, all the molecules of an object pass energy from one to another, until they are all hot.
Subduction
As the continents move toward each other, the sea floor between them is pulled beneath one of the plates.
What is Frequency (when discussing EM waves)?
The number of oscillations the wave undergoes in a certain amount of time
Continental Drift
According to Wegener’s hypothesis, the continents had once been joined to form a single supercontinent. Wegener also hypothesized that about 200 million years ago Pangaea (the name he called the supercontinent) began breaking into smaller continents; the continents then drifted slowly to their present positions. The movement of the continents to their present positions (continental drift), took place over millions of years.
Be able to define:
- solar eclipse
- lunar eclipse
- asteroids
- meteroids
- meteorites
- meteors
- comets
- earth> moon> sun
- moon> earth> sun
- large rocky objects in space (large asteroid belt between mars and jupiter)
- small rocky or metallic objects traveling through space
- are meteoroids that enter earth’s atmosphere
- streaks of light that trails behind meteorites as they burn up in earth’s atmosphere
- icy bodies that form trails as they are near the sun
Cells
• They are the basic unit of structure and function in living things.
• It may be specialized to fulfill specific functions within the organism. In animals, for example, red
blood cells carry oxygen to the rest of the body, while nerve cells transmit electrical impulses that carry information from one part of the body to another.
• Animal and plant cells contain smaller structures, called organelles, which are specialized to fulfill specific functions within the cell. Mitochondria, for example, break down glucose to provide energy to the cell. Bacterial cells lack most of these organelles.
• Animal and plant cells differ in several important respects. For example, all cells are surrounded by a permeable membrane, but plant cells are surrounded by a rigid cell wall, while animal cells are not. Plant cells also contain chloroplasts, an organelle which produces glucose through the process of photosynthesis.
Solar System
https://vimeo.com/5377648
What are cells?
The cell is considered the basic unit of life because it is the smallest structural unit of an organism that is capable of carrying out life processes including maintenance, growth and self-repair.
What is newton’s Third Law of Motion?
Newton’s Third Law states that all forces in the universe occur in equal but oppositely directed pairs; for every action, there is an equal and opposite reaction.
Rockets and jet planes capitalize on Newton’s Third Law. Each discharge hot gases in one direction (an action force so as to produce thrust (a reaction force). In both rocket and jet engines, chemical energy is changed to the energy of motion.
The waxy layer covering the exoskeleton of an insect is an adaptation that primarily aids in which of the following functions?
a. absorbing oxygen
b. avoiding detection by predators
c. minimizing water loss
d. blocking ultraviolet radiation
C. This question requires the examinee to apply knowledge of the characteristics of living organisms. In terrestrial insects, the waxy layer of the exoskeleton acts as a waterproof barrier that keeps water in and prevents insects from becoming dehydrated.
What is a compound machine?
two or more simple machines working together.
A wheelbarrow is an example of a complex machine that uses a lever and a wheel and axle. Machines of all types make work easier by changing the size or direction of an applied force.
What is the difference between an autotroph and a heterotroph?
Autotropic organisms are capable of harnessing energy from sunlight and using it to produce glucose, the main source of energy for the organism. Heterotropic organisms capture energy by eating plants or other animals.
What is respiration?
It is the process that transports oxygen from air to the cells and carbon dioxide in the opposite direction.
Cellular Respiration is the process in which nutrients are converted into useful energy within a cell.
What is Gravitational energy?
The energy possessed by a body because of its elevation (height) relative to a lower elevation is the energy that could be obtained by letting it fall to a lower elevation. For example, water at the top of a waterfall or stored behind a dam at a hydroelectric plant has gravitational potential energy.
What is metabolism?
It refers to the chemical reactions in the body’s cells that convert fuel from food into the energy needed to do everything from moving to thinking to growing.
What are the functions of Xylem and Phloem in vascular plants?
Xylem and Phloem are a system of tubes that are used to transport nutrients and water.
Frog Metamorphosis
Frogs hatch from eggs, develop into tadpoles, change into froglets, and mature as adults. Females typically lay large, jelly-like egg masses in the water. After a period ranging anywhere from a couple of days to 21 days, the embryo leaves its jelly shell and becomes a tadpole. The tadpole has a long tail and lives in the water. It has external gills like a fish and feeds on algae. Eventually, tadpoles begin to develop front legs and lungs for life on land. Once these develop, tadpoles, now commonly called froglets, begin their first investigations of land. In a short time, froglets lose their tails, grow into adults, and move to the land where they breathe with lungs.
Magnetism
A force that can attract (pull closer) or repel (push away) objects that have a magnetic material like iron inside them (magnetic objects).
A magnet is any object that has the ability to attract ferrous objects like iron, steel, nickel, and cobalt. Surrounding all magnets is a region called the magnetic field.
What energy generating pigment is found inside the choloroplast?
Chlorophyll
From Broadest (greatest number of organisms) to Narrowest (fewer number of organisms) what is the heirarchy of taxonomic ranks?
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
What are the four C’s of STEAM’s 21st Century Thinking?
Creativity, Collaboration, Critical Thinking, and Communication
Inner Planets
The closest to the sun, are solid spheres of rock; they include Mercury, Venus, Earth, and Mars. Generally smaller and denser than their counterparts. They also have few or no moons and no rings circling them.
In total, _____ elements have been observed as of March 2010, and new elements continue to be discovered. Of these, _____ occur naturally; the others are produced in laboratories.
118, 95
What are the three main types of rock?
Igneous, Sedimentary, Metamorphic
What is Mutualism?
In mutualism, members of two different species benefit by associating together. For example, many plant species require an animal to visit its flowers for pollination. The animal benefits in this relationship by having a source of food (nectar or pollen), while the plant benefits by having its ovules fertilized.
What is Newton’s Second Law of Motion?
Force = Mass times Acceleration (F=ma)
Any change in motion involves acceleration, or how much the velocity of an object changes in a certain time. The greater the mass of the object being accelerated, the greater the amount of force needed to accelerate the object.
What are the 4 basic types of human tissue?
connective, epithelial, muscle, and nerve.
What is Parasitism?
In parasitic relationships, one species receives a benefit from the relationship to the detriment of the other species. For example, there are parasitic fishes, such as the lamprey, that attach themselves to other fishes and suck their body fluids. Similiarly, tapeworms may attach to the intestines of host humans in their intestines. They constantly take in nutrients and can eventually cause organ and tissue damage.
What are organelles?
Smaller structures inside plant an animals cells, which are specialized to fulfill specific functions within the cell.
Mitochondria, for example, break down glucose to provide energy to the cell. Bacterial cells lack most of these organelles.
What is convection?
Convection is the transfer of heat in a gas or liquid by the circulation of currents from one region to another. In convection, the molecules get heated and rise up; the cold molecules sink and get reheated. Then they rise again to continue the cycle.
What is complete metamorphosis?
When an insect goes through all stages of change: egg > larva > pupa > adult
Phase Changes between States of Matter
Freezing: the substance changes from a liquid to a solid.
Melting: the substance changes back from the solid to the liquid.
Condensation: the substance changes from a gas to a liquid.
Vaporization: the substance changes from a liquid to a gas.
Sublimation: the substance changes directly from a solid to a gas without going through the liquid phase.
Deposition: the substance changes directly from a gas to a solid without going through the liquid phase.
Earth formed of 4 Layers:
Crust: solid plates ~5-30 miles thick
Mantle: hot, semi-solid rock, ~1,800 miles thick, causes the plates to move
Outer Core: liquid iron and nickel ~1,400 miles thick
Inner Core: solid ball of iron and nickel, ~700-800 miles in diameter
What are the 3 type of interactions of the eaths continental and oceanic plates?
Convergent: Coming together; makes mountains, volcanoes —-> <—-
Divergent: spreading apart; makes rivers, streams <—- —->
Transform: slides in opposite direction
What are the three steps in the life cycle of a plant?
Germination (Growth), Reproduction, Seed Production
What is Nuclear Energy?
Nuclear energy is stored in the nucleus of an atom—the energy that holds the nucleus together. Energy is released when nuclei are combined or split apart. Einstein showed that this energy is equivalent to mass. Nuclear power plants produce energy by splitting the nuclei of uranium atoms through a process called nuclear fission.
Galaxy
It is a system of stars, dust, and gas held together by gravity.
Rock Cycle
Weathering, Erosion, Rocks are Created, Changed and Destroyed
Steps in the Scientific Method
ask a question
research the topic
form a hypothesis
experiment
collect and analyze the data
draw conclusion
What is the Law of Conservation of Matter?
Atoms are neither gained nor lost during a chemical change.
While matter can neither be created nor destroyed in a chemical reaction, however, a new substance is formed, and there may be accompanying clues that a chemical reaction has taken place, such as light, heat, color change, gas production, odor, or sound
The relationship between form and function is a common theme in science. For example, the specific type of chemical bonding between copper atoms is what is responsible for the high electrical conductivity and ductility of this metal. Which of the following is another example of this relationship?
a. the expression of human genes in bacterial cells
b. the differences in weathering patterns caused by wind and water
c. the shape of plant leaves in the understory of a tropical rain forest
d. the jigsaw puzzlelike characteristics of the continents
C. This question requires the examinee to recognize the relationship between form and function. Plant leaves in the understory of a tropical rain forest are usually large in order to capture as much sunlight as possible, and they often have drip tips to help excess precipitation run off.
Science is Real!
https://vimeo.com/5377031
Light Year
It is the distance that light travels in a vacuum in a year—about 5.88 trillion miles.
What is the law of Reflection?
the angle of incidence equals the angle of reflection. Scattering is merely a reflection from a rough surface. Incoming light waves are reflected at many different angles because the surface is uneven.
Your students have been growing plants and measuring the growth per week. You want them to graph this data to show the small changes over time. What is the best type of graph to use?
- Bar Graph
- Pie Chart
- Line Graph
- an X-Y Plot
- Line Graph
Line graphs are used to track changes over periods of time. When smaller changes exist, line graphs are better to use than bar graphs. Line graphs can also be used to compare changes over the same period of time for more than one group.
What is electromagnetic (EM) radiation?
EM radiation is a family of waves generated by accelerating electric charges. For example, if an electric charge oscillates back and forth, it will radiate energy in the form of an electromagnetic wave. The quickness, or frequency at which charges oscillate, determines the type of electromagnetic radiation produced.
Visible light is one example of EM radiation, as are X-rays, microwaves and radio waves.
The entire rnage of EM waves is referred to the ElectroMagnetic Spectrum.
From “longest” to “shortest” wavelengths: radio waves, microwaves, infrared, visible, ultraviolet, X-rays, and gamma-rays.
Label the parts of this plant cell
What is a compound?
Compounds are groups of two or more elements that are bonded together through chemical change.
Organs
- Organs are made up of tissues that work together to perform a specific activity.
- Examples of organs include heart, brain, and skin.
There are 11 organ systems in the human body. Name them. (First or few few letters provided. If you feel confident, cover that part and list them!) Bonus if you can list each system’s primary function.
- C_
- D_
- En_
- Ex_
- Im_
- In_
- M_
- N_
- Rep_
- Res_
- S_
- circulatory
- digestive
- endocrine
- excretory
- immune
- integumentary
- muscular
- nervous
- reproductive
- respiratory
- skeletal
What is radiation?
Radiation is the transfer of energy by electromagnetic waves through space. Sunlight is a form of radiation that is radiated through space to our planet through a vacuum.
The total number of neutrons and protons in an atom is the what?
atomic number, which determines its mass.
