Chemistry Unit 2.1: Atomic Structure

Atomic Structure notes from all google slides.

Democritus

Was the first person to think about an atom's existence.

Democritus believed

matter is composed of atoms, tiny indivisible particles

Democritus didn't have

experimental evidence to support his thoughts.

Aristotle was

A very famous and popular Greek philosopher who rejected the idea of atoms

Aristotle was so influential that

he was able to have Democritus' ideas rejected

But Aristotle and Democritus both agreed that

matter is made of basic components.

John Dalton

developed modern atomic theory

Dalton's Atomic Theory 1st Point

All elements are composed of indivisible particles called atoms.

Dalton's Atomic Theory 2nd Point

Atoms of the same element are identical. The atoms of any one element are different from those of another. (This is partially incorrect, as Isotopes exist.)

Dalton's Atomic Theory 3rd Point

Atoms of different elements mix or combine in whole number ratios.

Dalton's Atomic Theory 4th Point

Chemical reactions occur when atoms separate, join, or rearrange.

In a chemical reaction, atoms of one element NEVER

change into another.

Cathode Ray Tube Experiment was made by J.J Johnson. In the experiment there was

A tube with inert gas, and two plates, a positive and a negative.

The particles in the gas were attracted to the

positive plate.

Therefore, the particles MUST

have a negative charge.

J.J. Thomson

Discovered the electron

J.J. Thomson had believed that the atom was ____________________________________________________________ from his experimental evidence.

a solid positive sphere with electrons shoved into the sides of it.

JJ Thomson Model was named

Plum Pudding Model

Robert Millikan

used the oil-drop apparatus to determine the charge of an electron

The mass of an electron is at least

1000 times smaller than the lightest atom. The mass of the electron is negligible.

Ernest Rutherford

Gold foil experiment

Ernest Rutherford used the gold foil experiment to

discover the nucleus.

Ernest Rutherford had shot high energy beam of

alpha particles into gold foil.

Most of the alpha particles went through he concluded...

The atom is mostly empty space.

Few particles were deflected at small angles he concluded...

The alpha particle came close to something small and positive (nucleus).

Very rarely particles were deflected at large angles he concluded...

The alpha particles hit a small, very dense, and positively charged center (nucleus).

Niels Bohr's Atom

electrons orbit in energy levels around the protons in the nucleus like our solar system.

Erwin Schrödinger

Electron cloud model: doesn't stay in fixed orbits, rather stay in a three dimensional space.

Electrons do not follow

fixed orbits.

Electron Bohr vs Electron Cloud

Electron Bohr stays in fixed orbits like the the solar system, it doesn't diverge from it's path. While an electron cloud is a three dimensional region, the energy levels still exist, but they don't orbit in fixated states.

Werner Heisenberg

Developed an uncertainty principle

uncertainty principle

we cannot determine the speed and position of the electrons around the nucleus.

quantum mechanics theory

electrons are found in specific orbitals

James Chadwick

discovered the neutron.

neutron

no charge

Atomic Number

the number of protons in the nucleus of an atom

An atomic number is always

a whole number

number of protons is equal to

number of electrons

the number of protons

will never change

Atomic Mass

The average mass of all the isotopes of an element

An Atomic Mass

will have a decmial

Atomic Number Vs Atomic Mass

Atomic Number is above the element, the mass is below.

Mass Number

Number of protons and neutrons combined

The atomic mass number is always

a whole number

Neutrons =

mass number - atomic number

The oxygen mass number is 16 and its atomic number is 8, what is the number of neutrons

8

Isotopes

Atoms of the same element that have different numbers of neutrons

Isotopes are

chemically alike

Isotopes have

different mass numbers

Hyphen Notation

Element-mass number

Isotopic Notation

A symbol that identifies the isotope of an element

Atomic Mass

The average mass of all the isotopes of an element

Atomic mass formula

Convert percentage back to decimal,

Multiply decimal with mass number

Add products of each isotope together

Chlorine has two common isotopes, with the mass of 35.45 amu (75.00% abundance) and 37.29 amu (25.00% abundance) What's the Atomic Mass?

35.91

What if you do not have the percentage or the atomic mass

Calculate the atomic mass of one of indium's isotopes (there are two)

If the atomic mass of indium is 114.8200 amu and one isotope of indium has a mass of 114.9041 amu and an abundance of 95.795%, whats the atomic mass?

113 amu

Atomic #

# of protons = # of electrons (neutral atoms)

Mass #

protons + neutrons

Neutrons

mass # - atomic #

Ion

An atom or group of atoms that has a positive or negative charge.

How do ions form

When an atom gain or lose electrons

How to write an ionic charge

An ionic charge is written as a sign (positive '+' or negative '-') followed by a number.

What does the number represent in an ion

the amount of electrons gained or lost

cation

A positively charged ion

metals lose electrons to become

cations

Cations have the same name as the element that forms them but

different chemical properties

Anions

negatively charged ions

Nonmentals tend to form ions

by gaining electrons

The name of the anion is the element name

with "ide" on the end

Ions Abbreviations