sherm unit 1-3

Independent variable

The variable that is intentionally changed in an experiment

Dependent variable

The variable that responds to the independent variable

Constant

A factor that remains the same throughout an experiment

Hypothesis

A proposed explanation for an observation

Conclusion

Compares experimental results to the hypothesis

Observation

Information gathered through senses or measurement

Physical change

A change that does not alter a substance’s identity

Chemical change

A change that produces a new substance

Physical property

A characteristic observed without changing composition

Chemical property

A characteristic describing how a substance reacts

Atom

Smallest particle of an element retaining its properties

Proton

Positively charged particle in the nucleus

Neutron

Neutral particle in the nucleus

Electron

Negatively charged particle in the electron cloud

Atomic number

Number of protons in an atom

Mass number

Total number of protons and neutrons

Isotope

Atoms of the same element with different numbers of neutrons

Most abundant isotope

Isotope closest to the atomic mass

Democritus

Greek philosopher who proposed atoms

Dalton

Proposed modern atomic theory

Thomson

Discovered the electron using cathode ray tube

Rutherford

Discovered the nucleus with gold foil experiment

Chadwick

Discovered the neutron

Millikan

Measured electron charge using oil drop experiment

Solid

Definite shape and volume

Liquid

Definite volume, no definite shape

Gas

No definite shape or volume

Sublimation

Solid directly to gas

Deposition

Gas directly to solid

Homogeneous mixture

Uniform composition throughout

Heterogeneous mixture

Non-uniform composition

Solution

Homogeneous mixture with smallest particles

Filtration

Separates solid from liquid

Density

Mass divided by volume

Density formula

D = m ÷ V

Intensive property

Independent of amount (density)

Extensive property

Depends on amount (mass, volume)

Cation

Positive ion formed by losing electrons

Anion

Negative ion formed by gaining electrons

Ionization energy

Energy required to remove an electron

Electronegativity

Ability of an atom to attract electrons

Atomic radius

Size of an atom

Trend across a period

Radius decreases, electronegativity increases

Trend down a group

Radius increases, ionization energy decreases

Alkali metals

Group 1 elements

Alkaline earth metals

Group 2 elements

Halogens

Group 17 elements

Noble gases

Group 18 elements

Representative elements

s and p block elements

Transition metals

d block elements

Reactants

Left side of chemical equation

Products

Right side of chemical equation

Law of conservation of mass

Mass is conserved in reactions

Celsius to Kelvin

K = °C + 273

Kelvin to Celsius

°C = K − 273

Significant figures

Indicate precision of measurements

Leading zeros

Not significant

Trailing zeros after decimal

Significant

Metal properties

Malleable, ductile, good conductors

Nonmetal properties

Brittle, poor conductors

Lab goggles

Worn when using chemicals, heat, or glass

Tongs

Used to pick up hot glass or metal

Fume hood

Removes toxic fumes

Aufbau principle

Electrons fill lowest energy orbitals first

Hund’s rule

Electrons fill orbitals singly before pairing

Pauli exclusion principle

No two electrons share same quantum numbers

Aufbau exception

Chromium and copper favor half-filled orbitals

Quantum mechanics

Describes motion of subatomic particles

p orbital shape

Dumbbell-shaped

Maximum electrons in 5th energy level

50

Wavelength and energy relationship

Inversely proportional

Current atomic model

Quantum mechanical model

Electron configuration of bromine

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

Orbital diagram rule

Fill orbitals singly before pairing

Energy formula

E = hc ÷ λ

Wavelength formula

λ = c ÷ ν

X-ray radiation

Very high frequency electromagnetic radiation

Abbreviated electron configuration

Uses noble gas core

Rhenium configuration

[Xe] 6s2 4f14 5d5

Valence electrons of antimony

5

Alloy

A mixture of metals

Unpaired electrons in selenium

2

Charge of aluminum ion

3+

Barium nitride formula

Ba3N2

Magnesium oxide formula

MgO

Phosphide ion

P3-

Overall charge of ionic compounds

Zero

Octet rule

Atoms gain or lose electrons to reach 8 valence electrons

Metallic bonding

Sea of delocalized electrons

FCC coordination number

12

Simple cubic coordination number

6

Strongest covalent bond

Triple bond

Carbon–sulfur bond

Nonpolar covalent

Molecular compounds

Can exist in any state at room temperature

Hybridization of GeS2

sp

Lone pairs on As in AsBr3

1

Polarity of BrO2

Polar

Single bond composition

1 sigma bond

Network solids

Lack intermolecular forces

Dipole-dipole force

Occurs in polar molecules