Chemistry Final 🙂🔫

almost done (thank goodness)(my brain hurts))

significant 0s

• leading 0s are never significant

• if a decimal is present, trailing 0s are significant

  • ex. 800 vs 800.

measurement

always must estimate one digit past that which you know

• if + or - with different levels of precision, you must round so the answer has the same amount of decimal places as the number with the least

• if x or / with different levels of precision, you must round so the answer has the amount of sig figs as the number with the least

precision

how consistent data is

accuracy

how close data is to accepted value

percent error

scientific notation

moving the decimal so #s are shorter (can be smaller or bigger)

• _ x 10ⁿ

metric prefixes

dimensional analysis

used to convert among units

atom

consists of e- cloud with negatively charged e- that have negligible mass very far away from a nucleus

nucleus

positive protons + neutral neurons

• p+ and n⁰ both have a mass of 1 amu

protons

identify element

• positive

• 1 amu

neutrons

hold together nucleus

• neutral

• 1 amu

electrons

participate in chemical reactions

• negative

• 1/1840 amu

atomic number

# of protons (c)

mass number

# of protons + # of neutrons (d)

element symbol

identified by p+ (a)

net charge

# of protons + # of electrons (b)

isotopes

same element, different masses

ions

same element, with net charge

• losing e- = positive charge (cation)

• gaining e- = negative charge (anion)

average atomic mass

weighted average of isotope masses

mole

a name for a #

Avogadro’s number

# of things in a mole (6.022 × 10²³)

molar mass

the mass of one mole of a substance

waves

wavelength + frequency

• low energy: long wavelength + low frequency

• high energy: short wavelength + high frequency

Planck’s constant

6.626 × 10^-34 Jxs

photoelectric effect

light can cause metals to release e-

• ability to release e- depends on wavelength, not intensity of light

• proves that ligh behaves as not only waves, but particles called photons

Bohr model

• excited H atoms release specific wavelengths (not a full spectrum)

• e- must exist only at specific energy levels

• emission spectra makes sense only for H+

• every element has a unique emission spectrum

• e- absorbs photons of specific energy

  • rise to higher shell (“excited”) state

• e- falls back to “ground” state

  • release photons of specific energy

Quantum Mechanical Model

e- exists in orbitals within s (1), p (3), d (5), & f (7) subshells

• each orbital holds 2 e-

orbital diagrams

use to fill in the e-

• s block (columns 1-2 + column 18, row 1) ← starts with 1s

• p block (column s13-18 except row 1) ← starts with 20

• d block (columns 3-12) ← starts with 3d

• f block (lanthanides + actinides) ← starts with 4f

Aufbau principle

fill orbitals in order

Hund’s rule

don’t pair up until you have to

Pauli Exclusion principle

electrons in the same orbital need opposite spins

valence electrons

e- in the outermost shell

core electrons

not valence electrons (not in outermost shell)

electron configuration

starts with last term, then builds up from it

noble gas configuration

start with nearest previous group 8A element (noble gases), add e- that come after

electron configuration of ions

main group elements take valence configuration of nearest noble gas

• atoms lost valence e- first (s and p)

The Periodic Table

• developed by Mendeleev

• organization:

  • groups (columns) & periods (rows)

  • metals, metalloids, and nonmetals

  • s & p block (main group), d block (transitional metals), f black (inner transitional metals)

Mendeleev

developed the Periodic Table

periodic law

elements grouped by similar, recurring properties (not order by mass)

Moseley

discovered the atomic #

metals

• solid

• ductile

• metallic lustre

• brittle

• semi-conductors

  *bottom left of Periodic Table*

metalloids

properties of both metals and nonmetals

• metallic lustre

• brittle

• semi-conductors

  *staircase down from B*

nonmetals

can be solid, liquid, and gas

• dull

• brittle

• insulators

  *top right of Periodic Table*

alkali metals

outer level electrons - 1

• G1

• very reactive

• soft

• silvery

• shiny

• low density

  ex. Li, Na, K, Rb, Cs, Fr

alkaline earth metals

characterized by loss of 2 e-

• G2

• harder & denser (than alkali metals)

• Be doesn’t react with water

• Mg only reacts with steam

• Ca, Sr, Ba, Ra react with water

  ex. Be, Mg, K, Ca, Sr, Ra

halogens

• G7

• nonmetals (not conductive)

• brittle & crumbly when solid

• poisonous & smelly

  ex. F, Cl, Br, I, As, Ts

noble gases

• G8

• stable

• colorless

• odorless

• inert

  ex. He, He, Ar, Kr, Xe, Rn

transitional metals

when ionizing, typically loses the 2s e- first

• d block

• good conductors

• harder/denser with higher melting points

• less reactive

inner transitional metals

f block

• lanthanides

• actinides

lanthanides

all similar in properties

• shiny metals

• similar reactivity of alkaline earth metals

• elements 58-71

actinides

all radioactive

• first 4 are found naturally, the rest are lab-made

• elements 90-103

effective nuclear charge

change of p+ minus shielding effect by e- (Zeff)

• when Zeff is higher, it’s harder to remove an e- because it’s being more attracted AND if Zeff is higher, the valence e- are pulled in more resulting in a smaller atomic radius

atomic radius

measure of the size of an atom

• atoms get bigger with more shells & as the valence e- get further away they’re less attracted by the nucleus (Zeff also has a smaller effect)

ionization energy

energy required to remove an e-

electronegativity

ability to attract e- in a chemical bond

metallic character

trends with low ionization energy

reactivity

• most reactive metals have low ionization energy

• most reactive nonmetals have high ionization energy

octet rule

atoms form bonds, needs 8 e- to satisfy it

• duet for H+

ionic bonding

nonmetals (high electronegativity) pull electrons from metal (low ionization energy)

• forms crystal lattice

covalent bonding

two nonmetals/metalloids (similar electronegativities) share e- to satisfy octet rule

metallic bonding

“sea” of delocalized valence e- amid metal cations

• explains electrical conductivity & malleability of metals

network solids

huge covalent molecules with very high melting points

crystal lattice

“formula units” (not molecules), lattice energy

lattice energy

energy released when ions stick together

• increase with increasing charge of ions

• decreases with increasing size of ions

bond lengths

average distance between nuclei

bond strength

energy required to break

Lewis structure

• line represents 2 shared e-

• total bonding & nonbonding e- = sum of atoms valence e-

• satisfy octets with lone pairs and/or double/triple bonds

• resonance

resonance

when Lewis structures have alternating single-double bond pattern, equivalent structure can be drawn

geometry

valence shell e- pair (VSEPR) theory

• e- repel, causing bonds & lone pairs to be as far apart as possible

steric number

# of atoms + lone pairs

• single/double/triple bonds: each count for 1 group

electron pair geometry

3 options:

• linear (180º)

• trigonal planar (120º)

• tetrahedral (109.5º)

molecular geometry

lone pairs cause different names

bond angles

if there are lone pairs, add “<“

bond polarity

from unequal sharing of e-

• bond is polar if the electronegativity difference is >0.4

molecular polarity

from unequal sharing of e-

• bond dipoles can “cancel” if symmetrical

net dipole moment

exists when molecule is asymmetrical (pos → neg)

• for steric #s of 2-4, lone pair will always result in this

ionic compounds

metal + nonmetal

• binary: 2 elements (-IDE ending)

• ternary: at least 3 elements (-ITE, -ATE)

• hydrogen adds an H+ to the formula, charge becomes less negative

stock system

use Roman numerals to indicate charge of ion

• can use with almost all d/f block + Sn + Pb

  • exceptions: Ag²⁺, Cd²⁺, Zn²⁺

covalent compounds

two nonmetals/metalloids

• when naming use a prefix for every atom except if the first atom only has one

molecular acids

H+ is always written first (except H₂O)

• binary: hydro __ic acid

• ternary: H⁺ + polyatomic ion

  • -ITE → -OUS

  • -ATE → -IC

acid formula

• formula begins with H+

• made up of nonmetals

• type of molecule compound (inorganic)

formula mass

sum of the average atomic masses of each element represented in the formula

• amount of element x atomic mass of element (same things for any other elements, then add all of them together)

percent composition

part/whole x 100 (used as conversion factor)

hydrates

contains H₂O in the compound, water + other molecules

• weight of H₂O: 18.02 g (leave as is for calculation)

empirical form

gives ration of elements in compound (ionic)(not actually #s of arrangement of atoms)

molecular form

actual formula of a compound (multiple of empirical formula)

chemical reaction

indicators

• color change

• temperature change

• formation of gas or precipitate

balancing

• only change coefficients, never subscripts

• don’t balance until you’ve made the correct products

synthesis

one product

• ex. A + B → C

decomposition

one reactant

• ex. C → A + B

single replacement

element replaces element in compound

• ex. AB + C → AC + B

double replacement

ions in two compounds swap partners

• ex. AB + CD → AD + CB

combustion

hydrocarbon + O₂ → CO₂ + H₂O

diatomics

consisting of two elements: Br, I, N, Cl, H, O, F

• only elements can be this

activity series

specifically single replacement; can predict whether an element will react with an anion

• if a metal/nonmetal is more active it’ll react w/ a less active ion

• why reactions are non reversible

• nonmetals activity series: F, C, O, Br, I, S, P

stoichiometry

based on the law of conservation of mass; the amount of products and reactants in a reaction

• mole-mole, mole-mass, mass- mole, mass-mass, molecules, molecules, etc.

percent yield

actual/theoretical x 100

actual yield

might not end up with the exact amount of product you hoped for

theoretical yield

everything goes into 100

limiting reagent

whatever is less abundant/runs out first; prevents more of the molecule from being formed

• the reagent in short supply limits the quantity of product that can be produced