Final Exam CH101

Avogrado’s number

6.022×10²³ units/mol

limiting reagent

reagent that can make the least product

chemistry

study of matter and the changes it undergoes

science

the branch of knowledge explored by means of the scientific method

Dalton’s Atomic theory

1. the smallest unit of an element is an atom

2. atoms combine to form molecules

3. Atoms are not changed during the course of a chemical reaction

matter

anything that has mass and takes up space

energy

the capacity to do work

potential energy

stored energy (chemical bonds)

kinetic energy

the energy of motion (thermal, electric, nuclear)

spontaneous reactions

releases energy as the substances move from a higher energy to a lower energy state

Coulomb’s Law of Force

• when the charges of two particles are both positiive or both negative, the force is positive and repulsive

• when one particle is positively charged and the other is negatively charged, the force is negative and attractive

strongest force

when both large charge and atoms are close together

Rutherford’s Nuclear Theory

• gold foil experiment

• directed alpha particles (He2+_ at gold foil

• some alpha particles were “deflected” by something in the atom

• devised a theory to explain the experimental results

• demonstrated that the nucleus consists of positvely charged protons

isotopes

atoms of the same element which have the same number of protons and electrons, but different numbers of neutrons

radio waves

hertz; wavelengths as long as football fields, used to transmit communication signals

microwaves

efficiently absorbed by water, cooking, medical imaging

infrared(IR)

heat; used in commerical night vision equipment

Visible

seen by human eyes

Ultraviolet (UV)

high energy; can break chemical bonds

x-ray

applied to medical uses, higher energy than UV

gamma rays

most energetic, destroys practically everything in its path

radio waves, microwaves, infrared, visible, uv, x-rays, gamma rays

orderof electromagnetic spectrum

light

• form of energy called electromagnetic radiation

• exists as a wave

frequency

how many waves pass a given point in one second

inversely

how are frequency and wavelength related?

directly

how are energy of light and frequency related?

bohr model of the atom

• electrons can orbit the nucleus only at specific distances or energy levels

• all orbits are negative in energy relative to an electron that does not sense the nucleus

• the n=1 orbital is closest to the nucelus and lowest in energy

• the energy gaps between the orbitals are not equally spaced

long arrow

high energy, high frequency, short wavelength

short arrow

lower energy, lower frequency, longer wavelength

up

aborption arrows

down

emission arrows

uv light

absorption arrows begin at 1 and emission arrow ends at 1

blue visible light

absorption arrow begins at 2 and emission arrow ends at 2, higher energy than red

red visible light

absorption arrow begins at 2 and emission arrow ends at 2, lower energy than blue

infrared light

absorption arrow begins at 3 or 4 and emission arrow ends at 3 or 4

probability region

described by 4 quantum numbers:

n, l, m_l, m_s

n principal QN

designates level or shell

primary indicatior of electron’s energy

can have integrer values 1,2,3

l orbital angular momentum QN

designates orbital shape (# of nodes)

secondary indicator of electron energy

can have values of 0,1,2,3…n-1

adds complexity that the Bohr model lacked

m_l magnetic orbital QN

designates the orientation of the orbitals of the sublevels

indicates the number of orbitals in a sublevel

can have integer values of l to - l

m_s spin QN

relates to spin

can only be +1/2 or -1/2

rules for ground state (lowest energy)

1. electrons enter the lowest energy available orbital

2. The Pauli Exclusion Principle: No two e- can have the same 4 QN (two objects cannot occupy the same space)

3. Hunds Rule: electrons occupy different orbitals in a sublevel with the same spin, rather than pair, until each orbital has at least one electron

ground state

all e-’s at lowest energy. e—’s in the same sublevel spread out as much as possible. Unpaired e-’s pointing the same direction.

excited state

an e- with an empty slot below it OR unpaired e=’s pointing in different directions OR a sublevel with paired electrons and empty orbital

not allowed

two e-’s in the same box pointing the same direction

elements in the same group

• same outer electron configuration

• react similarly

core electrons

• tightly bound, inner e-s

• filled lower energy levels

• unaffected by chemical reactions

valence electrons

outermost “s” electrons in partially filled sublevels

• loosely bound outermost 3-s

• outer shell (2s, 2p)

• involved in chemical bonding

effective nuclear charge

• attraction to nucleus felt by electron

• more protons = electrons get pulled in closer

• Zeff

Bottom left

large size, low EN, low IE

top right

small size, high EN (excpt noble gas), high IE

Zeff trend

top left (smallest) to bottom right (largest)

increases with atomic #, with a drop between rows

IE: first ionization energy

energy needed to remove an electron

electronegativity

attraction of an atom for bonding electrons

vacancies

attraction for incoming e-

ionic

non-directional. Held together by electrostatic charge (+ and -)

covalent

directional. sharing of electrons between atoms (often uneven sharing)me

metallicd

non-directional. cations connected in a “sea” of electrons

nonmetal

gains electrons to become an anion

metal

loses electrons to become a cation

charge on cation

# of e-s lost

family #

charge on anion

#e-s gaine

family # -8