chem topic 2: the atom

Subshells

different shell/sublevel types within a shell (s, p, d, f)

properties all isotopes share

- electron configuration
- number of protons
- reactivity (almost) cause of electrons

quantum of energy

the discrete amount of energy required to move an electron from one energy level to another. appears as a photon (certain wavelength of light)

Orbitals

a region in an atom where there is a high probability of finding electrons

why is energy of an electron quantized

they cannot change energies in continuous ways because they have to hop between orbitals

sublevel

Regions of space that electrons occupy make up a principal energy level. (n = 1, 2, 3, 4)

ground state

the lowest allowable energy state of an atom. most stable

energy levels (shells)

the fixed energies an electron can have. 1 has s sublevel 2 has s, p etc

Maximum number of electrons within a shell

2n^2 where n=shell #

Why does ionization energy increase across a period?

Moving left to right, the radius of the atom decreases as the increased number of protons protons pull on more electrons cause they are closer to the nucleus, and therefore feel the pull more strongly. It is harder to pull electrons away from these smaller atoms.

inconsistencies in ionization energy's increase across a period

- has to do with the spin direction symmetry - a half filled orbital is much more stable and has a higher ionization energy cause it has a full outer shell

plum pudding

experiment with cathode ray tubes showed that atoms had negative subatomic particles. Proposed that they are embedded in a positively charged matter that is the rest of the atom

Rutherford model of the atom

experiment: a gold foil was hit with alpha particles which have a positive charge. some went straight through but some deflected. Rutherford concluded that the atom is mostly empty space. All the positive charge and almost all of the mass are concentrated in a small region called the nucleus. Rutherford could NOT explain an atom's stability.

How is atomic mass calculated?

To calculate the atomic mass of an element, multiply the mass of each isotope by its natural abundance, expressed as a decimal, and then add the products. (relative abundance)

differences between isotopes

- different number of neutrons = different mass
- different physical properties

light spectrum

Electromagnetic radiation arranged in the order of its wavelength. We cannot perceive infrared (slightly less energetic) or ultra- violet (slightly more energetic) light.

Why is white light called a continuous spectrum?

White light from the sun is called a continuous spectrum because it is made up of all colors in the visible light spectrum (ROYGBIV)

What do all electromagnetic waves have in common/different?

- All travel at the speed of light in a vacuum
- but they differ in wavelength

the number of waves that pass a given point per second

frequency (Hz)

energy of a photon

the energy difference between two energy levels cause its the result of moving between them. e = hf

excited state electron

electron has absorbed energy and "jumped" to a higher energy level, farther from the nucleus

atoms form stable ions that

matching the electron configuration of the closest noble gas (octet rule)

Relative atomic mass

The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

number of orbitals in a subshell

s - 1, p - 2, d - 3, f - 4. each orbital can hold two electrons

ionization energy

the minimum energy required to remove an electron from an atom in its gaseous state

why is ionization energy measured in the gaseous state

it is isolated when gaseous, instead of solid/liquid in which it is bonded cause it would have a super high i.e.

Why does ionization energy decrease down a group?

Since there are new layers being added the valence electrons are farther from the nucleus and therefore the nucleus has a weaker hold on those electrons so they are easier to remove (less energy)

shielding effect

the reduction of the attractive force between a nucleus and its outer electrons due to the blocking effect of inner electrons

Pauli Exclusion Principle

states that a maximum of two electrons can occupy a single atomic orbital but only if the electrons have opposite spins. this is cause

Hund's Rule

orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spinWhen electrons occupy different orbitals, they are further apart, which minimizes repulsion between them. By filling degenerate orbitals singly, the atom reduces the repulsive forces between electrons.

Lower Energy Configuration: A configuration with less electron repulsion is lower in energy and more stable.