BIOLOGY 101 CHAPTER 2 | BIOLOGY
STUDY GUIDE, KEY CONCEPTS, PRACTICE
QUESTIONS, ANSWERS & EXAM PREP
Matter - correct answer anything that has mass and occupies space
Matter exists in three states - correct answer solid, liquid, and gas
abiotic - correct answer non living
biotic - correct answer living
98% of body weight of organisms are primarily composed of six elements - correct
answer carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur—acronym
CHNOPS
Atomic Structure - correct answer Atom is the smallest unit of an element
Atoms composed of subatomic particles:
Protons - correct answer positive charge; weight of 0, found in the nucleus
Neutrons - correct answer no charge; weight of 1, found in the nucleus
Electrons - correct answer negative charge; weight of 0; found in electron shell
Atomic Symbols - correct answer Each element is represented by one or two letters to
give them a unique atomic symbol
H = hydrogen, Na = Sodium, C = Carbon
Atomic mass - correct answer protons and neutrons
Atomic number - correct answer proton and neutrons
Vertical columns - correct answer groups; outermost electron #; chemically similar
Horizontal rows - correct answer periods; orbits/valence electrons; larger and larger
Isotopes - correct answer Atoms of the same element with a differing numbers of
neutrons (and therefore have different atomic masses). e.g. see carbon below
Characteristics of Isotopes - correct answer Radioactive
Give off energy in the form of rays and subatomic particles
Can be used as tracers
, Mutagenic - Can cause cancer
Medical use of Isotopes - correct answer MRI, CT, Nuclear Medicine Radiation can kill
cancer cell
Radiation can preserve food longer
Electrons and Energy - correct answer Atoms normally have as many electrons as
protons
Opposite charges balance leaving atom neutral
Electrons are attracted to the positive nucleus
Revolve around nucleus in orbitals
Can be pushed into higher orbitals with energy
Release that energy when they fall back to lower orbital
Different energy levels referred to as electron shells
Electron Orbitals - correct answer Innermost shell has two orbitals
Others have 8 or multiples
valence electron - correct answer outermost electron shell; how it reacts; most energy
If 3 or less - correct answer donate electrons
If 5 or more - correct answer Tendency to receive electrons
cation - correct answer An atom that loses an electron and becomes positively charged.
anion - correct answer An atom that gains an electron and becomes negatively charged.
Goal of atom - correct answer to become stable
Compound/ Molecule - correct answer when atoms of two or more different elements
bond together
CO2, H2O, C6H12O6, etc.
Characteristics dramatically different from constituent elements
Bonds - correct answer ties them together; exist between atoms in molecules contain
energy
Chemical Bonding - correct answer Bonds between atoms are caused by electrons in
outermost shells (VALENCE ELECTRONS)
chemical bonds - correct answer Unfilled electron orbitals allow formation of chemical
bonds, and atoms are most stable when each electron orbital is filled.
Covalent bond - correct answer Sharing of electrons; Each atom's unpaired electrons
are shared by both nuclei to fill their orbitals
STUDY GUIDE, KEY CONCEPTS, PRACTICE
QUESTIONS, ANSWERS & EXAM PREP
Matter - correct answer anything that has mass and occupies space
Matter exists in three states - correct answer solid, liquid, and gas
abiotic - correct answer non living
biotic - correct answer living
98% of body weight of organisms are primarily composed of six elements - correct
answer carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur—acronym
CHNOPS
Atomic Structure - correct answer Atom is the smallest unit of an element
Atoms composed of subatomic particles:
Protons - correct answer positive charge; weight of 0, found in the nucleus
Neutrons - correct answer no charge; weight of 1, found in the nucleus
Electrons - correct answer negative charge; weight of 0; found in electron shell
Atomic Symbols - correct answer Each element is represented by one or two letters to
give them a unique atomic symbol
H = hydrogen, Na = Sodium, C = Carbon
Atomic mass - correct answer protons and neutrons
Atomic number - correct answer proton and neutrons
Vertical columns - correct answer groups; outermost electron #; chemically similar
Horizontal rows - correct answer periods; orbits/valence electrons; larger and larger
Isotopes - correct answer Atoms of the same element with a differing numbers of
neutrons (and therefore have different atomic masses). e.g. see carbon below
Characteristics of Isotopes - correct answer Radioactive
Give off energy in the form of rays and subatomic particles
Can be used as tracers
, Mutagenic - Can cause cancer
Medical use of Isotopes - correct answer MRI, CT, Nuclear Medicine Radiation can kill
cancer cell
Radiation can preserve food longer
Electrons and Energy - correct answer Atoms normally have as many electrons as
protons
Opposite charges balance leaving atom neutral
Electrons are attracted to the positive nucleus
Revolve around nucleus in orbitals
Can be pushed into higher orbitals with energy
Release that energy when they fall back to lower orbital
Different energy levels referred to as electron shells
Electron Orbitals - correct answer Innermost shell has two orbitals
Others have 8 or multiples
valence electron - correct answer outermost electron shell; how it reacts; most energy
If 3 or less - correct answer donate electrons
If 5 or more - correct answer Tendency to receive electrons
cation - correct answer An atom that loses an electron and becomes positively charged.
anion - correct answer An atom that gains an electron and becomes negatively charged.
Goal of atom - correct answer to become stable
Compound/ Molecule - correct answer when atoms of two or more different elements
bond together
CO2, H2O, C6H12O6, etc.
Characteristics dramatically different from constituent elements
Bonds - correct answer ties them together; exist between atoms in molecules contain
energy
Chemical Bonding - correct answer Bonds between atoms are caused by electrons in
outermost shells (VALENCE ELECTRONS)
chemical bonds - correct answer Unfilled electron orbitals allow formation of chemical
bonds, and atoms are most stable when each electron orbital is filled.
Covalent bond - correct answer Sharing of electrons; Each atom's unpaired electrons
are shared by both nuclei to fill their orbitals
