chem exam 1

what is a mixture?

a mixture is 1+ substances physically combined

what is a homogenous mixture?

a homogenous mixture is uniform throughout, you cannot distinguish different parts of it.

what is a heterogenous mixture?

a heterogenous mixture is not uniform throughout, you can visibly and microscopically see differences.

pure substance

both elements and compounds are pure substances

element

an element cannot be broken down into smaller substances

compound

a compound is 2+ different elements chemically bonded

which experiment demonstrated electrons exist in atoms?

thomson's cathode ray tube experiment demonstrated electrons exist in atoms

which experiment determined the charge of the electron?

robert millikan’s oil drop experiment determined the charge of the electron

which experiment discovered the nucleus?

rutherford’s gold foil experiment discovered the nucleus

isotope

same element, different number of neutrons, must have same number of protons

heisenberg uncertainty principle

it is impossible to know precisely both the position and momentum of an electron

which particle has the smallest mass?

the particle with the smallest mass is an electron

speed of light

c = 3.00 × 10^8 m/s

density

D=m/v

energy

6.626×10^-34 J·s

nm

1m = 10^9nm

balmer/rydberg

λ1​=R(1/n²f - 1/n²i)

proton

positively charged particle; determines the element.

neutron

neutral particle; changing the number of neutrons creates an isotope.

electron

negatively charged particle; changing the number creates an ion.

atomic number

number of protons in an atom, top number

mass number

number of protons + neutrons, bottom number

finding neutrons

mass number − atomic number.

isotope

atoms of the same element with different numbers of neutrons.

3p³ orbital diagram

[↑] [↑] [↑][↑]\ [↑]\ [↑], with one electron in each orbital.

p orbitals

there are 3 orbitals in a p subshell.

hund's rule

electrons fill equal-energy orbitals singly before pairing.

electron filling order

1s→2s→2p→3s→3p→4s→3d→4p1s→2s→2p→3s→3p→4s→3d→4p.

ion

an atom with a different number of electrons than protons.

neutral atom

has equal numbers of protons and electrons.

J.J. Thomson

discovered the electron.

Rutherford

discovered that atoms have a small, dense nucleus.

Millikan

determined the charge of the electron.

Heisenberg Uncertainty Principle

you cannot know an electron's exact position and momentum at the same time.

Law of Multiple Proportions

the same two elements can combine in different small whole-number ratios to form different compounds.

electron falling to a lower energy level

releases a photon of light.

larger electron energy drop

produces higher-energy light with a shorter wavelength.