HOSA ATC BIOLOGY Chapter 2

Smallest unit of matter; composed of protons, neutrons, electrons

atom

Positively charged subatomic particle in the nucleus

proton

Neutral subatomic particle in the nucleus

neutron

Negatively charged subatomic particle moving around nucleus

electron

Electrical property that causes attraction/repulsion

charge

Central core containing protons and neutrons

nucleus

Pure substance made of atoms with same number of protons

element

number of protons; defines the element

atomic number

Atoms of same element with different numbers of neutrons

isotope

total number of protons + neutrons

mass number

Arrangement of elements by atomic number and properties

periodic table

Elements with full outer shells; chemically inactive

inert gases

Atoms → elements → isotopes → periodic table

basic building blocks

isotope with unstable nucleus that decays

Radioisotope

spontaneous emission of particles/energy

radioactive decay

detectable molecule used to follow biological processes

tracer

imaging technique using radioactive tracers

PET scan

dating fossils, tracing molecules, medical imaging

Uses of radioisotopes

Region where an electron is likely found

orbital

Energy level containing orbitals

electron shell

Unfilled space in outer electron shell

vacancy

Charged atom (lost/gained electrons)

Ion

Ability of atom to pull electrons

electronegativity

Formed when sodium loses an electron

sodium ion (na+)1

Formed when chlorine gains an electron

chloride ion (cl-)

attractive force between atoms

chemical bond

two or more atoms bonded

molecule

molecule with fixed ratio of different elements

compound

substances intermingle without bonding

mixture

atoms bond to fill vacancies and become stable

why atoms interact

attraction between oppositely chared ions

ionic bond

2 atoms share electrons

covalent bonds

electrons shared equally

nonpolar covalent bond

electrons shared unequally

polar covalent bond

diagram showing covalent bonds

structural formula

2 pairs of electrons shared

double bonds

3 pairs of electrons shared

triple bonds

weak attraction between polar molecules

hydrogen bond

water molecules stick to each other

cohesion

water sticks to other substances

adhesion

substance that dissolves others

solvent

water-loving;dissolves easily

hydrophilic

water-fearing does not dissolve in water

hydrophobic

water resists temperature change

temperature stabilization

released by acids in water

Hydrogen bonds (H+)

Measures H⁺ concentration

pH scale

Releases H⁺; pH < 7

acid

Accepts H⁺; pH > 7

base

Stabilizes pH by accepting/donating H⁺

buffer