Fessette - Unit 3: Atomic Structure

* the answers for the people are their contributions to atomic theory * flashcards are in order following the notes * sorry for the inconsistent capitalization but I am tired and didn't really know how to format this * good luck and text me if you have any questions! 🫡

Democritus (400ish B.C.E.)

Democritus (400ish B.C.E.)

The first person to suggest the existence of fundamental particles, also coined the term “atom”

John Dalton (1803-1805)

Had a self-named atomic theory that stated that all matter is composed of atoms (including elements), and that all atoms of a given element are completely identical

Law of Definite Proportions

(Identified by Dalton) Atoms can combine with each other in simple whole number ratios to form compounds

Law of Multiple Proportions

(Identified by Dalton) Atoms can combine in two or more ways to form compounds

J.J. Thomson (1906)

Discovered the electron using a cathode ray tube

Cathode Ray Tube

A glass tube that displays an electron beam that can be manipulated by a magnet, was used to discover electrons

Plum Pudding Model (Thomson’s Model)

Atomic model with electrons embedded in the nucleus

Ernest Rutherford (1911)

Conducted an experiment that proved that atoms had nuclei: Used a radioactive substance to shoot alpha particles at a sheet of thin gold foil surrounded by a film for the particles to display . The particles should’ve passed straight through but few deflected. They had come in contact with the nucleus!

Atomic Nucleus (Rutherford Model)

Atomic model with a positive nucleus with electrons floating around (mostly empty space)

Neils Bohr (1913)

Proposed that electrons orbit the nucleus at principle energy levels (PELs) and that electrons can move between these states through excitation and deexcitation

PEL

principle energy level

Planetary Model (Bohr Model)

Atomic model with a nucleus and PELs

excited state

when an atom absorbs heat or energy and an electron jumps to a higher PEL

ground state

the lowest PEL/the constant state of the atom

When electrons jump PELs, they release _______.

photons (colored light)

PEL equation

2n² = # of electrons

Erwin Schrödinger (1926)

Proposed that electrons move randomly in orbitals; their locations can never be accurately determined, there’s only a cloud of probability (an orbital) as to where they could be

Wave-Mechanical/Electron Cloud (Schrödinger’s Model)

Atomic model that includes a nucleus and a cloud of electron probability around it

AMU

atomic mass unit

What is the mass of a single proton?

1 AMU

What is the mass of a single neutron?

1 AMU

What is the mass of a single electron?

0 AMU

A proton has a _____ charge.

positive

A neutron has a _____ charge.

neutral/nonexistent

An electron has a _____ charge.

negative

Atomic Number

equals the amount of protons in a single element’s atom and determines the type of element an atom is

Mass Number

equals the amount of protons and neutron in a single element’s atom and is the total mass of the singular atom (always a whole number!)

Atomic Mass

the average mass of all atoms of an element in the universe (note that this value is an estimate because we can’t actually measure the mass of every single atom ever)

Valence Electrons

The number of electrons in the outermost PEL of an element’s atom

Kernel Electrons

The number of all the electrons besides the valence electrons

Lewis Structures/Dot Diagrams

symbols that represent the number of valence electrons of an atom

Bonding Sites

locations on a PEL where there is only a single electron that allows atoms to attach or lose their electrons

Isotopes

Atoms of the same element that have different amounts of neutrons

Ions

Atoms of the same element that have different amounts of electrons and now have positive or negative charges

how to solve for atomic mass

(% occurrence converted to a decimal) x (mass number of isotope) = atomic mass of isotope

add the number of results of these (how many depends on how many isotopes) together and sigfig

anion

negatively charged ion (gained an electron)

cation

positively charged ion (lost an electron)

make sure to review notes and stuff and look at the work packet and try to enjoy studying!

woop woop thanks