Chapter 2 - Atoms and Elements Flashcards
Which machine can you use to pass a sharp metal tip over a flat metal surface, which allows you to scans the surface on an atomic scale? (Essentially taking pictures of atoms on the surface)
Scanning Tunneling Microscope (STM)
Other than taking pictures of atoms on the surface, what does the STM allow you to do?
It allows you to move individual atoms across the surface
- Total mass of the material you have before the reaction must equal the total mass of material you have at the end
- total mass of reactants = total mass of products
Law of Conservation of Mass
All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements
• Law of Definite Proportions
If a 10.0g sample of calcite contains 4.0g of calcium, how much calcite contains 0.24g of calcium?
0.60g of calcite
When 2 elements form 2 different compounds, the masses of B that combine with 1g of A can be expressed as a ratio of small, while numbers
Law of Multiple Proportions
Carbon combines with oxygen to form two different compounds. Carbon monoxide contains 1.33g of oxygen for every 1.00g of carbon. Carbon dioxide contains 2.67 g of oxygen for every 1.00g of carbon. What would the oxygen mass ratio be?
It would always be 2 since carbon dioxide is twice as big as carbon dioxide
2.67g / 1.33g = 2
- Each Element is composed of tiny, indestructible atoms
- All atoms of a given element have the same mass and properties
- Atoms combine in simple, whole-number ratios to form molecules of compounds
- In a chemical reaction, atoms of one element cannot change into atoms of another element (they simple rearrange the way they are attached)
Dalton’s Atomic Theory
Is the statement correct ACCORDING TO DALTONS THEORY:
1) Copper atoms can combine with zinc atoms to make gold.
2) Water is composed of many identical molecules that have one oxygen atom and two hydrogen atoms.
1) Incorrect. According to Dalton, atoms of an element cannot turn into atoms of another element by chemical reaction.
2) Correct. According to Dalton, atoms combine together in compounds in small whole number ratios.
Opposite charges _____
Ex: - and +
Attract
Like charges _____
• Ex: + and +
Repel
To be neutral, something must have no charge or ____
Equal amounts of opposite charges
A glass tube containing metal electrodes from which almost all the air has been evacuated
Cathode Ray Tube
What were the results of the J.J. Thomson’s Cathode Ray Tube Experiment?
- Cathode rays are made of tiny particles that have a negative charge (beam deflected towards the + plate)
- The amount of deflection was related to the charge and the mass of the particles
- Atoms are Not unbreakable
Cathode Ray particles became known as _____
Electrons
Tiny negatively charged particles found in all atoms
Electrons
What part of an atom was missing in Thomson’s Plum Pudding Atom?
The positively charged Protons
Certain elements constantly emit small, energetic particles and rays, which could penetrate matter
Radioactivity
Ernest Rutherford discovered that there were 3 different kinds of emissions:
Alpha (a) rays, beta (b) rays, and gamma (g) rays
Made of particles with a mass 4x H atom and + charge
Alpha (a) rays
Made of particles with a mass 1/2000th H atom and - charge
Beta (b) rays
Energy rays, not particles
Gamma (g) rays
What were Rutherfords Conclusions after his Gold Foil experiment?
- Atoms are mostly empty space, since most particles went straight through
- Atoms contain dense particles that are small in volume but large in mass, since a few particles bounced back
- The dense particle is positively charged, since some particles experienced large deflections
The ____ had essentially the entire mass of the atom
Nucleus
The nucleus is _____ charged
Positively charged
For an atom to be neutral, there must be equal number of _____ and ____
Protons and Electrons
The neutrally charged particle found in the nucleus alongside the proton is called the ____
Neutron
The number of protons and in the nucleus is called the ___
Atomic number
The Elements are arranged on the Periodic Table in order of their ____
Atomic numbers
Soddy discovered that the same element could have atoms with ____ ____, which he called isotopes.
Different masses
All isotopes of an element are chemically ____ and undergo ____ chemical reactions.
Identically, the same
Isotopes are identified by their ____ ____, which is the sum of the number of protons and neutrons.
Atomic mass
Charged atoms or groups of atoms are called ____
Ions
When atoms gain electrons, they become negatively charged ions, called ____
Anions
When atoms lose electrons, they become positively charged ions, called
Cations
Ions behave much differently than the ____ atoms
Neutral
Because materials such as table salt are neutral, there must be ____ amount of charge from cations and anions in them
Equal
Nonmetals form which kind of iconic structure?
Anions
Anions are named by changing the ending of the name to
- ide
* Ex: fluorine = fluoride ion
Metals form which kind of ionic structure?
Cations
How are cations named?
- The same as the metal
* Ex: Sodium = Sodium ion
When the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically.
Periodic Law
What is Mendeleev known for?
- Ordering elements by atomic number
- Periodic Law
- Putting elements with similar properties in the same column
- Using the patter to predict properties of undiscovered elements
- Rearing order where properties did not fit
What are some of the qualities of Metals?
- Solids at room temperature
- Reflective surface
- Conduct heat
- Conduct electricity
- Malleable (can be shaped)
- Ductile (can be drawn or pulled into wires)
- Lose electrons and form cations
- About 75% of elements
- Lower left on the Periodic Table
What are some qualities of Nonmetals?
- Found in all three states of matter
- Poor conductor of heat
- Poor conductor of electricity
- Solids are brittle
- Gain electrons in reactions to become anions
- Upper Right on the table (expect H)
What are some qualities of Metalloids?
- Show some properties of metals and some of nonmetals
- Also known as semiconductors
- Ex: Silicon (shiny, conducts electricity, does not conduct heat well, brittle)
What is the Modern Periodic Table set up like?
Elements with similar chemical and physical properties are in the same column.
1) Columns on the Periodic Table are called _____
2) Rows on the Periodic Table are called ____
1) Groups or Families
2) Periods
What does each period show?
Each period shows the pattern of properties repeated in the next period.
Main Group:
Representative Elements = A Groups.
Transition Elements:
B Groups = All metals.
What are some of the qualities of Hydrogen?
- Nonmetal
- Colorless, diatomic gas
- Low melting point and density
- Reacts with nonmetals to form molecular compounds (ex: H20)
- Reacts with metals to form hydrides (transport hydrogen)
- HX dissolves in water to form acids
What are some examples of Alkali Metals?
- Lithium (Li)
- Sodium (Na)
- Potassium (K)
- Rubidium (Rb)
- Cesium (Cs)
What are some qualities of Alkali Metals (Group IA)?
- Soft, low melting points, low density
- Flame Test: Li = Red, Na = Yellow, K = Violet
- Very reactive, never find unconvinced in nature
- Tend to form water-soluble compounds
- React with water to from basic (alkaline) solutions and H2
What are some qualities of Alkali Earth Metals (Group IIA)?
- Harder, higher melting point, and denser than alkali Metals
- Flame Test: Ca = Red, Sr = Red, Ba = Green
- Reactive, but less than corresponding alkali metal
- Form stable, insoluble oxides from which they are normally extracted
- Oxides are basic = Alkaline Earth
- Reacts with water to form H2
What are some examples of Halogens?
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)
- Astatine (At)
What are some qualities of Halogens (Group VIIA)?
- Nonmetals
- F2 and Cl2 are gases, Br2 liquid, I2 solid
- All diatomic
- Very reactive
- Cl2 and Br2 react slowly with water
- React with metals to form iconic compounds
- HX all acids
What are some qualities of Noble Gases (Group VIIIA)?
- All gases at room temperature
- Very low melting and boiling points
- Very unreactive
- Very hard to remove electron from or give electron to (do not wish to interact)
For many main group metals, the charge =
The group number
For nonmetals, the charge =
The group number - 8
Masses and abundance’s of isotopes are measured with a
Mass spectrometer
A ____ ____ is a graph that gives the relative mass and relative abundance of each particle.
Mass Spectrum
What is the formula for atomic mass?
Fractional abundance of isotopes x mass of isotopes
Find the atomic mass for Gallium if Ga-69 with mass 68.9256 amu and abundance of 60.11% and Ga-71 with mass 70.9247 Amy and abundance of 39.89%.
69.72 amu
When is mole day?
23rd October from 6.02 am to 6.02 pm.
The number of atoms of an elements sample is called
Mole
What is equal to 1 Mole?
6.022 x 1023
A silver ring contains 1.1 x 1022 silver atoms? How many moles of silver are in the ring?
1.8 x 10^-2 mol Ag
The number of particles in 1 mole is called
Avogadro’s Number
What is Avogadro’s Number?
6.0221521 x 1023
The molar mass of an element in grams is numerically ____ to the element’s atomic mass in amu.
Equal
The lighter the atom, the ___ a mole weighs
Less
The slighter the atom, the ____ atoms are in 1 g.
More
Calculate the moles of carbon in 0.0265 g of pencil lead
0.0265g C x 1 mol / 12.01g
= 2.21 x 10^-3 mol C
How many copper atoms are in a penny weighing 3.10 g?
2.94 x 10^22 atoms Cu
