Physical Chemistry – Test #1

Equation for working out maximum amount of electrons in a shell.
#e = 2n(squared)
How many maximum electrons could there be in the first four shells.
2 , 8 , 18 , 32
Why do electrons spin around the nucleus?
Electrons are always trying to get away from the nucleus but they are attracted to the proton so it goes around (orbits) the nucleus.
When you head to the right of the periodic table, what happens to the size of the atoms.
The atom becomes smaller because there are more protons and electrons which means there is a bigger attraction and therefore the atom in more closely bunched together and it makes a smaller atom.
Mass No. / Atomic Mass
Known as ‘A’. Total number of Protons and Neutrons in the element’s atom.
Atomic Number
Known as ‘Z’. The periodic table number as well as the number of protons in the nucleus.
Uncharged atom
Means the amount of protons and electrons are the same
How to right symbols?
A
x
Z
Elements
Consist of only one type of atom
Compounds
Consists of different types of elements chemically bonded together.
Who discovered the periodic table and when?
Mendeleev created the first periodic table in 1869. He has the element Mendeleev named after him.
What are the natural elements?
The first 92 elements are natural. The ones after 92 man made often named after famous scientists or planets.
Columns
Known as groups and each group 1-8 has different numbers of valence electrons.
1 – Alkali
2 – Earth Alkali
3 – Halogens
4 – Noble Gases
Rows
Known as periods, when periods go down in the table the elements increases in orbitals.
Names of the electron shells
1st shell – K
2nd shell – L
3rd Shell – M
4th Shell – N
Sub Shells
Within each shell there are sub shells with different energy levels and these fill according to these energy levels.

1st Shell – 1 shell
2nd Shell – 2 sub shells
3rd Shell – 3 sub shells
4th Shell – 4 sub shells

What are the names of the blocks on the periodic table
S block (Alkali and Earth Alkali)
D block (Transition Metals)
P block (Far right)
F block (Man-made bottom block)
How many maximum valence electrons can each block carry?
S: 2
P: 6
D: 10
F: 14
Isotope
Variation of an element with different amount of electrons.
Average atomic Mass
The average mass of a certain element’s atom as it varies due to different isotopes with different masses.
Relative Formula Mass
The total mass of a compound. Find the atomic mass of the elements in that compound (multiply the atomic mass of an element if there is more than one atom of that element in the compound). Then add the total mass of each elements together to get the relative formula mass. RFM.
Relative Percentage Mass
Calculating the percentage of mass for a certain element within a compound.
AMU
Atomic Mass Unit
Calculating RPM
Get the total mass of an element within in a compound and divide it by the total mass of the compound (relative formula mass).
Calculating Relative Abundance
X/100 (x Atomic Mass) + 100-x/100 (x Atomic Mass) = RAM
Relative Abundance
The amount of an element or isotope within a compound or element.
Empirical Formula
The approximate amount of each element within a compound where the quantity of an atom is written on the bottom right of the atom’s symbol.

Eg. H20, C6S12P4

How do you work out the empirical formula for a compound?
First you must have either the percentage of each of the elements to the compound or the masses (weight) of the elements. Then divide them each by their atomic masses and have them as a ratio. Then divide each number by the lowest number in the ratio. After that round the ratios to whole numbers. Then right the element’s symbols and quantities together to form the compound’s symbolic name.
What is the order of the electron sub-shell structure across the first four rows of the periodic table?
1s2 , 2s2, 2p6 , 3s2, 3p6 , 4s2 , 3d10 , 4p6.
What is the bohr configuration?
The basic form of writing electron structure.

E.g.

2,8,1
2,8,6
2,6 etc.

When does the elements stop filling according and start filling out over different shells even though a previous shell isn’t yet full?
After element 18 (Argon). After argon it then goes 2,8,8,1 instead of 2,8,9. This is because of an overlap in electron orbits causing electrons to fill out different and not in order.
Who developed the idea of the atom and when
Democritus in 360 BC. He called it ATOMA.
John Dalton
In 1808 he suggested that all matter was made up of tiny spheres that could bounce around with perfect elasticity and called them atoms.
Joseph John Thompson
In 1898 he Found that atoms could sometimes eject a far smaller negative particle which he called an electron. He developed the plum pudding model in 1904 where electrons were scattered unevenly with an elastic sphere surrounded by a soup of positive charge to balance the electrons.
Er
Ernest Rutherford
Oversaw Geiger and Marsden carrying out his famous experiment.

they fired Helium nuclei at a piece of gold foil which was only a few atoms thick.

they found that although most of them passed through. About 1 in 10,000 hit

They found that while most of the helium nuclei passed through the foil, a small number were deflected and, to their surprise, some helium nuclei bounced straight back.

Rutherford’s new evidence:
Rutherford’s new evidence allowed him to propose a more detailed model with a central nucleus.

He suggested that the positive charge was all in a central nucleus. With this holding the electrons in place by electrical attraction

However, this was not the end of the story.

Niel Bohr
studied under Rutherford at the Victoria University in Manchester. Bohr refined Rutherford’s idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons.
Why does an element have +2 etc.
Because it had lose two electrons to get a full shelled and gains a charge of +2. All periodic table elements are uncharged forms so the protons and electron amounts are the same.
James Chadwick
In 1932: studied under Rutherford and Geiger in 1913 at the Technical University of Berlin In 1932, while working at Cambridge University, discovered the neutron by bombarded beryllium with alpha particles and noticed that a non-ionising radiation was emitted
Current periodic table
Made by Glenn Seaborg and his research team at Berkley Univeristy in California
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