Chemistry Midterm Review

atomic radius

half the distance between 2 nuclei of 2 identical atoms that are bonded together

as you move down a group in the periodic table, the atomic radius _______? why?

increases; valence electrons are in the higher energy levels (farther away), therefore, not as strongly attracted to the nucleus, inner electron shield valence electrons from the median pull(blocking)

as you move across a period in the periodic table, the atomic radius _______? why?

decreases; effective nuclear charge increases as we go across a period, so electrons are strongly attracted to the nucleus

a cation is _______ than the corresponding neural atom. why?

smaller; the same nuclear (#p+) can pull fewer amount of electrons more effectively toward the nucleus > smaller size.

an anion is _______ than the corresponding neutral atom. why?

larger; an anion has the same charge but increased # of electrons so its harder to pull close to the nucleus (electron repulsion = larger size)

ionization energy

opposite of atomic radius; energy needed to remove an electron from a gaseous atom

as you move down a group in the periodic table, the ionization energy _______. why?

decreases; because the size of the atom increases and the valence electrons are further away form the nucleus and are easier to remove

as you move across and period in the periodic table, the ionization energy _______. why?

increases; atoms get smaller across and period and electrons are strongly attracted to the nucleus and therefore are harder to remove > more energy is needed

chemical bond

the force that holds two atoms together and makes them function as a single unit

bond energy

the energy needed to break a bond, its magnitude determines the strength of the bond

ionic bonds

metals + nonmetals

ionic bonds are formed by _______ .

electrons transferred from metals to nonmetals

covalent bonds (polar and nonpolar)

2 or more nonmetals

covalent bonds are formed by _______ .

electrons shared (equal - polar; unequal - nonpolar)

metallic bonds

metal cation and electrons

metallic bonds are formed by _______ .

shared electrons

metals tend to form _______ and nonmetals usually form ________.

cations, anions

octet rule

stable "noble" gas configurations are achieved when atoms gain/lose electrons to have EIGHT valence electrons

molecule

group of atoms acting together (bonds) representing the smallest unit that participates in a chemical reaction

molecular formula

true formula for a molecule, represents # and types of atoms that are bonded together

_______ ________ are a type of structural formula and show which atoms are bonded to which other atoms in a molecule and how many electrons they share

lewis structures

lone pair (unshared pairs) of electrons

electrons that are not bonded (1 or 2 dots)

double bond

in order to achieve on octet, sometimes atoms have to share 2 electrons

triple bond

in order to achieve on octet, sometimes atoms have to share 3 electrons

exception to the octet rule: hydrogen and beryllium

only need 2 electrons and 4 electrons (H - 2, Be - 4)

exception to the octet rule: boron and aluminum

only need 6 valence electrons

exception to the octet rule: phosphorous and sulfur

can have 8, 10, or 12 valence electrons

mono

1

di

2

tri

3

tetra

4

penta

5

hexa

6

hepta

7

octo

8

nona

9

deca

10

chemistry

study of matter and the changes it undergoes

matter

anything that has mass and takes up space

states of matter

solids, liquids, and gases

solid

definite shape, definite volume

liquid

indefinite shape, definite volume

gas

indefinite shape, indefinite volume

physical properties

characteristics that can be observed without altering the identity or composition of the substance

chemical properties

characteristics that can only be observed by changing the identity or composition of the substance

physical change

does not change the composition or identity of the substance

chemical change

does change the composition or identity of the substance

law of conservation of matter

matter is neither created nor destroyed; mass of the substances before the reaction = mass of the substance after the reaction

element

substances that cannot be broken down into any other substances

periodic table

a table which organizes the elements according to their chemical properties

compound

2 or more elements chemically conbined

pure substances

refers to elements and compounds; always has the same composition

mixture

combination of pure substances; had variable composition; these can be separated by physical changes

heterogenous mixtures

regions of the mixture are different(composition is not uniform; different parts can be distinguished)

homogenous mixtures

mixture is the same throughout (different parts cannot be distinguished)

filteration

separate solids from liquids (ex. tea bags)

distillation

separate liquids based on boiling point

crystillization

separate pure solids from impurities (rock candy)

chromatography

separate parts of a homogenous mixture (ink)

precision

how close 2 or more values are to each other

accuracy

how close a measured value is to the known value

density

mass/volume

absolute zero

the temperature at which all motion ceases; zero on the Kelvin scale (no negative temp for Kelvin possible)

Kelvin

°C + 273

energy

the ability to do work or produce heat

heat

the flow of energy between objects at different temperatrures

1 cal

4.184 J

4.184 J

1 cal

1 kcal & 1 Cal

1000 cal

temperature

a measure of the random motions in a substance

exothermic

a process that releases heat to the surroundings

endothermic

a process that absorbs heat from its surroundings

specific heat capacity

the amount of heat required to raise the temperature of 1 gram of a substance by 1°C

specific heat formula

Q = m x c x ΔT

calorie

the amount of heat required to raise the temperature of 1 gram of water by 1°C

percent error formula

((∣experimental - theoretical)/theoretical) x 100

atom

most basic fundamental unit of which elements are made of; smallest particle that retains the properties of the elements

nucleus

small, dense, + charged; contains protons + neutrons

protons

positively charged; relative mass of 1; relative charge of 1

electrons

negatively charged; relative mass of 1; relative charge of -1

cation

+ charged; formed by atoms losing electrons

anion

- charged; formed by atoms gaining electrons

balancing equations

the equalization of ions on the reactants side of an equation and the products on the other side of the equation

diatomics

H N F O I Cl Br

synthesis

A + B → AB

decomposition

AB → A + B

single replacement

A + BX → AX + B

double replacement

AX + BY → AY + BX

combustion

CXHY + O2 → CO2 + H2O

metal carbonate

metal oxide + CO2 → decompostion

metal chlorate

chop off excess O2 → decomposition

atomic mass

the mass of one atom of that unit (amu → atomic mass units)

formula mass

sum of the average atomic masses of each atom in a chemical formula

mole

SI base unit that measures an amount of matter. -6.022 × 10²³ (avogadro's #) particles (atoms, ions, formula units, molecules)

molar mass

mass in g of 1 mol of a substance containing 6.022 × 10²³ representative particles.

empirical formula

simplest formula containing the lowest whole # ratio of atoms present; may or may not be a true formula; all formulas are empirical

percent compostion

(part/whole) x 100

molecular formula

true formula for molecule; whole # molecule of empirical formula

molecular formula formula

molar mass of the molecule/empirical mass

stoichiometry

study of quantitative relationships between the amount of reactants by using a balanced equation