4.1.1.1 Atoms, elements and compounds

What is an atom

Radius of 1 x 10⁻¹⁰ m

All substances are made of atoms. An atom is the smallest part of an element that can exist.

What is the nucelus

Middle of the atom

Contains protons and neutrons

Radius of around 1 x 10⁻¹⁴m

Has a positive charge because of the mass

Most of the atoms mass Is concentrated in the nucleus

Electrons

Mass: 1/1800

Charge: -1

Move around the nucleus in electron shells

They’re negatively charge pd and tiny but they cover a lot of space

Proton

Mass:1

Charge: +1

Determines what element it is

Neutron

Mass: 1

Charge: neutral

Charge of an atom

Atoms are neutral- no overall charge

Because there are the same number of protons as electrons

The charge on the electrons is the same size as the charge on the protons but opposite so they cancel out

Mass​ ​number

the​ ​sum​ ​of​ ​the​ ​protons​ ​and​ ​neutrons​ ​in​ ​an​ ​atom

Atomic number

Number of protons

Isotopes

\:​ ​atoms​ ​of​ ​the​ ​same​ ​element​ ​with​ ​different​ ​numbers​ ​of​ ​neutrons and the same number of protons

What is an ion

An atom that has gained or lost and electron

What is an element

An element is a substance made up of only one type of atom, each with the same number of protons

How are atoms represented

Chemical​ ​symbols​ ​represent​ ​an​ ​atom​ ​of​ ​an​ ​element​ ​e.g.​ ​Na​ ​represents​ ​an​ ​atom​ ​of
sodium

How to calculate atomic mass (Ar)

Sum of (isotope abundance x isotope mass number) / sum of abundance of all isotopes

What is relative atomic mass

This is an average mass taking into account the different masses and abundances (amounts) of all isotopes that make up the element

What is molecules

2 or more atoms, held together by chemical bonds

What is a compound

Compounds​ ​contain​ ​two​ ​or​ ​more different ​ ​elements​ ​chemically​ ​combined​ ​in​ ​fixed​ ​proportions held together by chemical bonds

How can compounds be represented

​can​ ​be​ ​represented​ ​by​ ​formulae​ ​using​ ​the​ ​symbols​ ​of​ ​the​ ​atoms​ ​from​ ​which​ ​they were​ ​formed​ ​e.g.​ ​HCl​ ​is​ ​a​ ​compound​ ​containing​ ​1​ ​atom​ ​of​ ​hydrogen​ ​and​ ​1​ ​of​ ​chlorine per​ ​molecule

Ca(OH)2

Ca

OH

OH

Chemical reactions

Always involved in the formation of one or more new substances and often involve detectable energy change

making bonds involved at and giving away taken or sharing electrons I need the elections are involved

word equations

The molecules on the left hand side of the equation are called the reactants

The molecules on the right hand side are called the products

Not as quick as using chemical symbols, and you can’t tell what happened to each atom

Symbol equations

show atoms on both sides

Just show the symbols or formulas of reactants and products

Balancing equations

* There must always be the same number of atoms on both sides they can’t just disappear
* Your balance the equation by putting numbers in front of the formulas, where needed
* The formulas are all correct, but the numbers of some actions don’t match up on both sides
* You can’t change formulas, you can only put numbers in front of them