Chemistry- Unit 1 Test

Dalton’s theory

Dalton’s theory

his theory stated that all matter is made up of tiny, indivisible particles called atoms. He thought that all atoms were identical and atoms of different elements were different. He also thought that atoms formed new substances in chemical reactions,but they aren’t created/destroyed, but rather rearranged.

Thomson’s contribution

Using a cathode ray experiment, he discovered electrons which were 1000x lighter than atoms, which were negatively charged. He hypothesized that electrons were evenly dispersed in a positively charged sphere (plum pudding)

Rutherford’s contribution

He used an alpha particle emitter and pointed the matter at gold foil. Because some particles were repelled, he hypothesized that atoms must contain a small, positive dense central nucleus

Nuclear Model

the model that hypothesized that a nucleus consisted of positively charged particles called protons, with empty space around it containing electrons. This also predicted a third particle having no mass with the same mass as protons, which were confirmed as neutrons in 1932.

Bohr’s energy levels

His experiments led him to propose that electrons aren’t just anywhere in the empty space of a nucleus, but rather in specific orbitals/energy levels.

Planetary model/Bohr-Rutherford diagrams

Diagrams that show the number of protons, neutrons, electrons. There are only used for the first twenty elements.

octet rule

All elements that aren’t noble gases don’t have full valence shells are reactive. They typically gain full valence shells when atoms of elements combine to get 8 outer electrons

Forming ions

Ions are formed when electrons are lost or gained to complete the outer valence level

Cation

positive ions that are formed when an atom loses one or more electrons

Anion

negative ions that are formed when an atom gains one or more electrons

Multivalent

elements that can form more than one ion. They have multiple charges and are usually transitional metals

polyatomic ions

ions that consist of multiple atoms of more than one element

isotopes

atoms of the same element that have different numbers of neutrons

radioisotopes

isotopes that aren’t stable and break down; they can be described as radioactive

Mass number

an average of the masses of the different isotopes of an element

Group

a vertical column on the periodic table. Element in the same ———— have similar properties

Period

a horizontal column on the periodic table. ———— are organized in increasing atomic number

The periodic law

when elements are arranged in order of increasing atomic number, we see patterns that reoccur when certain elements are grouped together

atomic radius

the distance from the nucleus to just beyond the outermost electrons

effective nuclear charge

the force of attraction experienced by an atom’s electrons due to the positively charged nucleus

from left to right, atomic radius decreases b/c

each element has one more proton and electron than the element before it, but no new energy levels are created. this means there is less screening and a similar ratio of protons to neutrons, so the electrons are pulled closer and the radius is smaller

as you go down a group, the atomic radius increases b/c

energy levels are added from one period to the next and each new level is farther away from the nucleus. the inner energy levels also cause shielding of the nuclear charge. as a result, the outer electrons aren’t as attracted to the nucleus, making the radius larger

ionic radius of a cation is smaller than the radius of the same element b/c

the force of attraction is shared among fewer electrons, so the effective nuclear charge is slight stronger on each one, pulling them closer to create a smaller radius

ionic radius of an anion is greater than the radius of the same elements b/c

repulsion among electrons increases when more are added while the effective nuclear charge stays the same. this means each electron is pulled less strongly, creating a larger radius

ionization energy

the amount of energy require to remove one valence electron from an atom/ion in its gaseous state.

first ionization energy

the energy required to remove the most loosely held electron from an atom/ion

as atomic radius decreases, ionization energy tends to increase b/c

the effective nuclear charge is higher on elements with a smaller atomic radius, meaning that more energy is needed to remove an electron bc the force is greater

as you move down a group the ionization energy decreases b/c

the effective nuclear charge is less, meaning that its easier to detach an electron which equals lower ionization energy

electron affinity

the energy that’s released (energy change)when an electron is added to a neutral atom in its gaseous state

as you move from left to right, electron affinity increases b/c

as atomic radius decreases, the effective nuclear charge between the nucleus and the outermost electrons increases. this means that gaining another electron releases energy

as you move down a group electron affinity decreases b/c

the number of energy levels increases, meaning the effect nuclear charge is lower and the energy release would also be less

ionization energy and electron affinity are related b/c

ionization energy and electron affinity have the same rules regarding what is needed for a high/low value, so if ionization is high, electron affinity will be too and vice versa

ionic bond

a bond formed between a metal and a non metal that is held together by electrostatic force (positives and negatives attract)

molecular element

a substance composed of molecules made up of two or more atoms of the same element

molecular compound

a compound that’s usually made up of two or more non metals. they are held together by covalent bonds, which involves two atoms sharing electrons

electronegativity

the ability of an atom to attract electrons

ionic bond

a bond where the electronegativity difference is 1.7+. a large electronegativity means that one atom takes electrons from the other

non-polar covalent bond

a bond where the electronegativity is 0 and the element is molecular

polar covalent bond

a bond where elctronegativity is 0.5-1.7. this means that one atom attracts electrons more strongly than the other and electrons spend more time around the more electronegative atom

naming ionic compounds

metal goes first, non-metal ends in ide

naming ionic compounds with multivalent ions

use roman numerals to indicate which charge is being used, non-metal ends in ide

polar molecule

a molecule with a positive and negative pole

factors that determine if a molecule is polar

if the molecule has polar bonds and the shape of the molecule