Chem midterm

element

one type of atom, a substance that cannot be broken down into simpler substances by chemical means

compound

a substance made up of two or more different chemical elements combined in a fixed ratio

mixture

a compound made up of two or more chemical components that are not chemically linked

heterogeneous

a mixture in which the composition is not uniform throughout the mixture ex: ice cubes in soda, sugar and sand, salt and pepper, can be picked out and seen

homogeneous

one whose composition is uniform throughout the mixture ex: air, coffee, sugar water, rainwater, can’t be picked out or seen

accuracy

how close a measurement results comes to the true value

precision

a measure of how close a series of measurements are to one another

matter

anything that takes up space

chemistry

studies the composition and structure of matter

physical property

a characteristic that can be observed or measured without changing the identity of the substance ex: color, density, hardness, and melting and boiling points

chemical property

indicates how substance reacts with something being changed ex: flammability, toxicity, acidity, reactivity (many types), and heat of combustion

physical change

the original substance still exists, it only changed in form ex: melting an ice cube, boiling water, shredding paper

chemical change

an entirely new substance ex: Burning, cooking, rusting and rotting

mass

a measure of the amount of matter in a substance or an object

steps of scientific method

purpose, research, hypothesis, experiment, analysis, conclusion

sig fig rules

-Zeros between two non-zero digits ARE significant

-Leading zeros are NOT significant

-Trailing zeros to the right of the decimal ARE significant

-Trailing zeros in a whole number with the decimal shown ARE significant

Proton

P+, positive charge, relative mass: 1, in the nucleus

Neutron

n, 0 charge, relative mass: 1, in the nucleus

Electron

e-, -1 charge, relative mass: 1/1840, electron cloud outside the nucleus energy levels

atomic number

the number of protons in an element, it’s always a whole number, protons = electrons, lower left corner

mass number

number of protons and neutrons combined

isotope

atoms with the same number of protons but different numbers of neutrons

atomic mass

number will have decimal, it is the weighted average of all the elements isotopes, protons + electrons, upper left corner

How do you find the number of neutrons

Mass - protons

How do you find the charge

look at the atomic number, gaining is negative, losing is positive

Democritus

greek philosopher, first person to think of an atom, had no experimental evidence

J.J Thompson

cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. his plum pudding model of the atom had negatively-charged electrons embedded within a positively-charged "soup." discovered electron

Rutherford

used the gold foil experiment to discover the nucleus, shot a high beam of alpha particles into gold foil

John Dalton

discovered atomic theory

atomic theory

all elements are composed of indivisible particles

atoms of the same element are identical, the atoms of any one element are different from those of another

atoms of different elements mix or combine in the whole number ratios

chemical reactions occur when atoms separate, join, or rearrange in a chemical reaction

Isoelectronic

two atoms that have the same number

Hund’s Rule

each orbital must get one electron, before putting two electrons in any one orbital

Pauli Principle

atomic orbitals can only hold 2 electrons at most and must have opposite spins

Electron configuration

arrangement of electrons in a particular element

3D orientation

comes from atomic orbital

principle energy level

average distance of the electron to the nucleus

noble gas

gain or lose electrons to become a ————

Silly Penguins Dive For Goldfish

S: 1 orbital 2 electrons

P: 3 orbitals 6 electrons

D: 5 orbitals 10 electrons

F: 7 orbitals 14 electrons

G: 9 orbitals 18 electrons

Solid

definite shape, definite volume, does not flow

liquid

no definite shape, definite volume, flows

Gas

no definite shape, no definite volume, diffuses

hypothesis

reasonable explanation for what was observed

Scientific notation

make # between 1-9.99, moving to the right = neg

ex: 0.0000006.15 = 6.15 X 10^-7

Mass divided by Volume =

density

density X volume =

mass

Cations

biggest ——→ smallest

Anions

smallest ——-> biggest

Why is there a larger increase from 1st to 2nd I.E

second electrons are closer to the nucleus, therefore need more energy to be removed

Atomic radius

½ of the distance between the nuclei of two like atoms

The inner electrons

shield or block the attraction from the nucleus

this does not affect the magnitude of attraction from the nucleus due to this effect.

A.R, While there is an increase in number of protons down a group

orbital

as you move down the group each element has one more occupied

Proton

as you move across the period each element has one more

Ionization energy

the energy required to remove valence electron from a gaseous atom or ion

highest possible value for electronegativity

4.0, Fluorine

electronegativity

the tendency for atoms of the element to attract electrons when they are chemically combined with another element

in I.E, when you move down

it decreases because the valence electrons being further from the nucleus

in I.E, when you move across

it increases because of the increased effective nuclear charge I.E

a positive charge of an ion increases when

the size of an atom will decrease

a negative charge of an ion increases

the size of an atom will decrease

alkali metals

group 1

Noble gases

group 18

Nalogens

group 17

Alkali earth metals

group 2

metals

left of staircase, shiny, malleable, good conductor

non metals

right of staircase, dull, brittle, poor conductor

groups are numbered

1-18, vertical

Periods are numbered

1-7, horizontal

s and p blocks

representative elements

d block

transition metals

f block

inner transition metals

Ductile

made into wire

Nuclear charge

magnitude of attraction from nucleus