Biology: 2.1-2.3

matter

anything that has mass and takes up space; composed of atoms

every atom possesses an orbiting cloud of tiny subatomic particles called electrons moving around a core; at the center is a dense nucleus with protons and neutrons

what did Niels Bohr propose?

matter

anything that has mass and takes up space; composed of atoms

every atom possesses an orbiting cloud of tiny subatomic particles called electrons moving around a core; at the center is a dense nucleus with protons and neutrons

what did Niels Bohr propose?

atomic number

number of protons

have the same number of protons, exhibit the same chemical properties, and are said to be the same element

atoms with the same atomic number…

atomic mass

protons+neutrons

electrons

negatively charged; maintained in orbitals by attractions to positively charged nucleus

orbitals

region around nucleus with a high probability of containing an electron

spherical, dumbbell-shaped, and more

what can orbitals be shaped like?

no more than two electrons

how many electrons can each orbital contain?

neutral atoms

SAME number of protons and electrons, electrically neutral, and have no net charge

ions

atoms where the number of electrons does not equal the number of protons; charged particles

cation

atom with more protons than electrons; POSITIVE charge

anion

atom with fewer protons than electrons; NEGATIVE charge

isotopes

atoms that possess different numbers of neutrons

radioactive isotope

unstable and undergoes radioactive decay, releasing energy

• can label or “tag” a specific molecule and follow its progress

• subatomic particles emitted have potential to damage living cells

half-life

the time it takes for one-half of the atoms in a sample to decay

the number and arrangement of its electrons in their orbitals

what is the chemical behavior of atoms shown by?

less potential energy

when an electron is closer to the nucleus, it has __________ potential energy.

quantum

specific amount of energy

oxidation

loss of an electron by an atom or molecule in a chemical reaction

reduction

gain of electron in a chemical reaction

atomic number

what did Dmitri Mendeleev arrange known elements on the periodic table based off?

noble gases

have 8 electrons in their outer energy level

inert or nonreactive

halogens

have 7 electrons in their outer energy level

highly reactive

octet rule

atoms tend to establish completely full outer energy levels

organic compounds

contain primarily CHON (carbon, hydrogen, oxygen, and nitrogen)

molecule

group of atoms held together by energy in a stable association

compound

when a molecule has atoms of more than one element

ionic bond

atoms with opposite charges attract each other

TRANSFER

covalent bonds

when two atoms share one or more pairs of electrons

SHARING

no net charge, octet rule is satisfied, no unpaired electrons

when are covalent bonds stable? (3)

ionic bonds

what bonds form crystals?

electronegativity

more electronegative means nucleus has a greater pull on electrons

• upper-right corner has the highest of this

nonpolar

covalent bond that involves EQUAL sharing of electrons

polar

covalent bond where electrons are shared UNEQUALLY due to differences in electronegativity of the atoms involved

chemical reaction

formation and breaking of chemical bonds

temperature, concentration of reactants and products, and catalysts

the extent to which chemical reactions occur is influenced by? (3)

heat

what increases the rate of reaction?

more reactants —> more collisions —> faster reactions

what happens when there is more reactants?

catalyst

increases the rate of reaction, shortens the time needed to reach equilibrium

hydrogen bond

sharing of H atom

hydrophobic interaction

forcing of hydrophobic portions of molecules together in presence of polar substances

radioactive isotopes

these have an unstable nucleus that will spontaneously release energy in the form of radiation

groups

what on the periodic table has the same number of valence electrons?