Atomic Structure

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Atoms ,Elements ,Compounds and Mixtures

An atom is a molecule/ particle the makes up an element.

Atoms are the smallest part of pure substances called elements.

1nm=1x10 m

The radius of a atoms nucleus is less than 1/10,000 of the atom.

A compound is made when two or more elements are chemically bonded together.

A mixture Is where two or more elements are mixed together but are not chemically bonded together.

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Atomic Structure

Atoms are made up of protons ,neutrons and electrons

You will find protons ,neutrons in the nucleus of the atom and you find electrons in their outer shells of the atom.

Neutrons Change=0 (neutral) Mass=1 Electrons Charge=-1 Mass=very small Protons Change=+1 Mass=1

Golden rules:

~ Count the number of electrons using the element atomic number

~ The first shell of an atom it takes a maximum of two electrons

~ All the shells of the atom take a maximum of eight electrons

~ Keep filling your shells until you’ve used up all your electrons

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History of the Atom

Democritus:400 BC
Democritus said if you were to cut something in half again and again and again you would eventually get something to small to cut in half. He called it “uncuttable” which in Greek is Atmos that that is where the presentday term atom comes from.

John Dalton: 1808
Do you believe that Every element’s was the same size and mass. So he thought all actors were just tiny spheres.

J.J Thomson: 1897
He imagined a atom As a positively charged sphere with negative electrons stuck into it. He called his all of the atom “The Plum Pudding model”

Ernest Rutherford:1911
Ernest just wanted to test JJ Thomases model of the atom and he proved that the plum pudding model was wrong.

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History of the Atom

Neils Bohr:
Neils found out that electrons don’t randomly orbit the nucleus of the atom. I found out that they all put the nucleus in different energy levels called shells.

James knew that there were positive protons and negative electrons but he found out that there were another particle called neutrons. So he found out that neutron had the same mass as a proton.

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Isotopes

Isotope is a version of an element with a different number of neutrons put the same number of protons and electrons.

Many elements have more than one isotopes this means when referring to the masses of element relative atomic mass (Ar) is used.

This is an average mass taking it into an account for the differences masses of isotopes that make up the element and how abundant each isotope is (how much there is of it).This means it is not always helpful.

Relative atomic mass = sum of abundant x mass number of isotopes

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Periodic table

The group number tells you how many electrons are in the outer shell for example if an Element is in group 3 it has three electrons on its outer shell.

The period tell me how many shells are around the nucleus of the atom for example if an element was in period 4 that means it has 4 shells around it’s nucleus.

There are currently 100 elements in the periodic table that have been discovered.

Every element of the periodic table has a symbol with one or two letters and a relative atomic mass and atomic number.

These are the names of all the groups in the periodic table

Group 1: alkali metals.
Group 2: alkaline earth metals.
Group 11: coinage metals
Group5: pnictogens
Group 6: chalcogens.
Group 7: halogens.
Group 0: noble gases.

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