Chemistry Test 1

Avagadro’s Number

6\.022 \* 10^23 per 1 mole

Chemistry

study of matter and the changes it undergoes.

Science

branch of knowledge gained by the scientific method.

Antoine Lavoisier (18th century)

helped transform chemistry from a science observtion to the science of measurement.

Lavoisier

said matter is elements (cannot be broken down) or compounds (>1 element); helped Dalton for Atomic Theory

Law of Conservation of Mass

during a chemical reaction the total mass remains constant; “Nothing is lost, nothing is created, everything is transformed".”

John Dalton’s Atomic Theory

Atoms combine to form molecules; atoma are not changed in the course of a chemical reaction, they just “change partners”

atom

smallest component of an element composed of protons and neutrons surrounded by electrons.

Ex) Na, B, Fe

element

an atom or group of atoma of the **same** type.

Ex) Na, C, Fe, P_4, S_8

compound

two or more **different** atoms bound together.

Ex) CO_2 , H_2O

molecule

two or more atoms bound together.

Ex) P_4, S_8, CO_2, H_2O

diatomic molecules

The “gens”

Ex) hydrogen, nitrogen, oxygen, halogens, P_4 & S_8

two components of the universe

matter and energy

matter

physical objects that take up space, have mass atoms, elements, moleculesm compounds, …”stuff”

energy

the capacity to do work or transfer heat kinetic, potential

potential energy

stored energy, energy of position.

Ex) a truck on a hill; a cheese wheel on a hill; a stretched rubber band (each can be converted to kinetic energy).

Nature seeks to

release energy as substances move from higher energy to a lower energy state.

△E < 0

Unfavorable (unlikely)

a floppy rubber band becoming taut. (E final)

Favorable (likely)

a taut rubber band becoming floppy (E initial)

energy change

△E = E (final) - E (initial)

Coulomb’s Law of Force

1800s: Coulumb observed force of charged particles

if charges are f of particles 1 and 2 are both positive or both negative if the force is

positive & repulsive. (from Coulumbs force eqn.)

when one particle is positively charged and the other is negatively charged, the force is

negative & attractive. (from Coulumbs force eqn.)

larger numerator =

large charge

smaller denominator =

closer distance; less shielding (vacuum shields less than water)

particles are more attracted to one another when

they have larger charge and are closer together.

proton

a subatomic particle with a charge of +1 and an atomic mass of 1.

neutron

a subatomic particle with a charge of 0 and an atomic mass of 1.

electron

a subatomic particle with a charge of -1 and an atomic mass of \~0.

atomic number

the number of protons.

atomic mass or mass number

the number of protons and neutrons in an atom.

isotopes

atoms with the same atomic number (protons) but different mass numbers (neutrons different).

cation

a species with more protons than electrons (+).

anion

a species with more electrons than protons (-).

group

elements within the same column sharing similar properties.

period

elements in the same row.

metalloids

elements at border between metals & nonmetals that show properties intermediate between metals and nonmetals.

1903: Thompson “Plum/Rasin Pudding”

1911: Rutherford Nuclear Model

Visible light

extends from 400 nm to 700 nm.

Radio Waves

Hertz: wavelengths as long as football fields, used to transmit communication signals.

Microwaves

efficiently absorbed by water, cooking, medical imaging.

Infrared (IR)

Heat: used in commercial night vision equipment.

Visible

seen by human eyes.

Ultraviolet (UV)

High energy: can break chemical bonds.

X-rays

Applied to medical uses; can break chemical bonds.

Gamma rays

Most energetic, will seriously mess you up.

light

is a form of energy called electromagnetic radiation; light exists as a wave.

wavelength (lambda)

distance between 2 identical points on a wave

Unit = m

frequency (“nu”)

number of waves that pass ap point in one second.

Units = waves/second , 1/s , Hz , s^-1

longer wavelength

lower frequency (fewer waves per second)

shorter wavelength

higher frequency (more waves per second)

speed of light (c)

3\.0 x10^8 m/s

Photon of light

has energy directly proportional to the frequency of its wave.

Electrons

can orbit the nucleus only at specific **distances** or **energy levels**.

n=1 orbital →

closest to nucleus, lowest in energy.

As **n** increases

distance from nucleus and energy increases.

Energy gaps between orbitals are

**NOT** equally spaced, they move closer together as **n** increases.

Schrödinger equation

in behaving as waves, there are regions where electrons **will be found** regions where they **will NOT be found** (__nodes__).

“n” : Principle Quantum Number

designates energy level (or shell); primary indicator of the electrons energy; tells average distance from nucleus; n is always positive.

“l” : Angular Momentum Quantum Number

designates orbital shape; also dictates number angular nodes = l; __secondary__ indicator of electrons energy (sublevel or sub shell); ranges in (n-1, n-2, …, 0) and is also based on letter orbitals.

“m_l” : Magnetic Orbital QN

designates **orientation in space** of the orbitals of the sublevel “l”; indicates the **number** of orbitals ina sublevel; integer values range from “l” to “-l”

“m_s” : Spin QN

electrons are spheres of negative charge (kind of); when rotate on axes (“spin”), makes magnetic field; depending on rotation the fields can be directionally “up” or “down”; **one orbital** accomodates 2 **electrons** of opposite spin values: +1/2 or -1/2

Orbital Sublevels Ranked in Every

(n+l)

Aufbau (building up) principle

electrons enter first available orbital or lowest (all electrons at the lowest energy); Nature seeks the lowest energy state.

The Pauli Exclusion Principle

No two electrons have the same 4 QN; two objects can’t occupy the same space (electrons in the same sublever spread out as much as possible).

Hund’s Rule

electrons occupy different orbitals in a sublevel with the same spin, rather than pair, until each orbitaal has at least one electron; at the same energy sublevel, electron’s like to spread out and have the same spin, its the lowest energy state, pairing is higher energy (unpaired electrons pointing the same direction).

Finding number of electrons