Chapter 2 Flashcards
Living organisms and everything around them are composed of what?
Matter
A substance that cannot be broken down to other substances by chemical means
Element
What is matter?
Anything that occupies space and has mass
What are the three forms of mass?
- Solid
- Liquid
- Gas
How many elements do we know of today?
92
What is a compound?
A substance consisting of two or more different elements combined in a fixed ratio.
What for element make up about 96% of the weight of our bodies?
Oxygen
Carbon
Hydrogen
Nitrogen
What is a trace element?
An element that is essential for life but required in extremely minute amounts.
What is an atom?
The smallest unit of matter that retains the properties of an element.
Where does the name “atom” come from?
The Greek word meaning “indivisible”
What are the three subatomic particles we will be learning about?
- Proton
- Electron
- Nucleus
What is a proton?
A subatomic particle with a single positive electrical charge, found in the nucleus of an atom.
What is an electron?
A subatomic particle with a single negative electrical charge. One or more electrons move around the nucleus of an atom.
What is a neutron?
A subatomic particle having no electrical charge, found in the nucleus of an atom.
What is an atomic number?
The number of protons in each atom of a particular element.
Unless otherwise indicated an atom has an equal number of what?
Protons and electrons.
What is a mass number?
The sum of the number of protons and neutrons in an atom’s nucleus.
The mass of a proton and the mass of a neutron are measured in what unit of measurement?
The Dalton
What is atomic mass?
The total mass of an atom; also called atomic weight. Given as a whole number, the atomic mass approximately equals the mass number.
What is an isotope?
One of several atomic forms of an element, each with the same number of protons but a different number of neutrons.
What is a radioactive isotope?
An isotope whose nucleus decays spontaneously, giving off particles and energy.
What do biologists use as tracers?
Radioactive isotopes.
Mass amounts of what we’re released in Chernobyl.
Radioactive isotopes
What varies in electrons.
The amount of energy they possess
What are the energy levels that electrons move a around called?
Electron shells
What does the amount of electron shells depend on?
The element’s atomic number
What is discrete volumes of space where electrons are commonly found?
Orbitals
How many electrons can an orbital hold?
A maximum of two
What is the outermost electron shell called?
Valence Shell
What determines the chemical properties of an atom?
The amount of electrons in the valence shell
How do chemical interactions between atoms enable them to fill their outer electron shell?
Each atom will share, donate, or receive electrons.
How many covalent bonds can an atom form?
It depends on the amount of electrons needed to complete the outer shell
How many chemical elements are essential to life?
25
How many elements make up 96% of living matter?
Four
What elements make up 96% of living matter?
Carbon
Oxygen
Hydrogen
Nitrogen
What trace element is required by all organisms?
Iron (Fe)
What is required by an organism but only in minute amounts?
Trace elements
What is required for normal activity of the human thyroid gland?
0.15 mL of iodine
A type of weak chemical bond formed when the partially positive hydrogen atom participating in a polar covalent bond in one molecule is attracted to the partially negative atom participating in a polar covalent bond in another molecule (or in another region of the same molecule).
Hydrogen bond
A chemical bond resulting from the attraction between oppositely charged ions.
Ionic bond
A molecule containing polar covalent bonds and having an unequal distribution of charges.
Polar molecule
The making and breaking of chemical bonds, leading to changes in the composition of matter.
Chemical reaction
A starting material in a chemical reaction.
Reactant
An ending material in a chemical reaction.
Product
The sticking together of molecules of the same kind, often by hydrogen bonds.
Cohesion
The attraction between different kinds of molecules.
Adhesion
A liquid that is a homogeneous mixture of two or more substances.
Solution
The dissolving agent of a solution. Water is the most versatile solvent known.
Solvent
A substance that is dissolved in a solution.
Solute
A solution in which water is the solvent
Aqueous solution
A substance that increases the hydrogen ion (H) concentration in a solution.
Acid
A substance that decreases the hydrogen ion (H) concentration in a solution.
Base
A measure of the relative acidity of a solution, ranging in value from 0 (most acidic) to 14 (most basic). The letters pH stand for potential hydrogen and refer to the concentration of hydrogen ions (H).
pH scale
A chemical substance that resists changes in pH by accepting hydrogen ions from or donating hydrogen ions to solutions.
Buffer
Formed by sharing a pair of valence electrons by two atoms
Covalent bond
Chemicals are the things that make up what?
Our bodies
The bodies of organisms
The physical environment
Life first evolved in where?
Water
Imagine that you have been hired as a chemist and your first task is to examine a newly discovered atom. The paperwork you’re given states that it’s atomic number is 110. What does this mean?
The atom contains 110 protons
Radioactive isotopes are biological tools that are often used for what?
To detect brain tumors
For an atom to achieve maximum stability and become chemically inert, what must occur?
It’s outermost energy shell must be filled with electrons
The formation of ions involves what
Gain or loss of electrons
If a certain atom has a tendency to lose two electrons, this lends itself to the formation of a(n)?
Ion
Radioactive isotopes are biological tools that are often used to
Detect brain tumors
The formation of ions involves what?
Gain or loss of electrons
If a certain atom has a tendency to lose two electrons, this lends itself to the formation of an
Ion
