Atoms Flashcards
Average size of an atom
100 picometers
Proton
Positive nucleon with mass of 1
Neutron
Neutral nucleon with mass of 1.
Electron
A negative subatomic particle situated on a shell of an atom with a relative mass of 1/2000
Nucleon
Subatomic particles situated in the nucleus of an atom
Mass number
Number of protons and neutrons
Atomic number
Number of protons
How many protons are there in comparison to electrons in a neutral atom?
The number of electrons always equal the number of protons in a neutral atom
What happens if there’s an unequal number of electrons to protons?
The atom becomes charged and is an ion
Isotope
Different atomic forms of the same element, which have the same proton number but a different number of neutrons. (Same proton number but different mass numbers).
Molecule
A group of atoms
Relative atomic mass
The weighted mean mass of an atom. (Rounded to nearest 0.5 in periodic tables)
Relative abundance
How much there is of each isotope compared to the total amount of the element in the world. (Ratio, fraction or percentage).
First atomic model theory
Dalton’s billiard ball (1800’s)
What did Dalton’s billiard ball show?
All matter is made of atoms that can’t be broken down.
Different elements are different atoms.
Atoms are rearranged in chemical reactions.
Compounds are two or more atoms joined.
What was the second atomic model?
JJ Thompson’s plum pudding (1900’s)
What did the plum pudding model show?
That there was negative subatomic particles within the atom.
What was the third atomic model?
Rutherford’s nuclear atom 1900’s
What did Rutherford’s nuclear atom show?
That there was a nucleus within the atom.
What was the fourth atomic model?
Bohr’s electron orbits
What did Bohr’s model show?
That electrons had orbits.
That there were neutrons and free space within the atom.
Who Carried out the gold foil experiment and when?
Geiger and Marsden (Rutherford’s assistants) in 1911
What did the gold foil experiment compose of?
A vacuum with alpha radiation, a piece of gold foil and a detector
Why was it a vacuum in Geiger and Marsden’s experiment?
So that air particles wouldn’t get in the way
What happened during Geiger and Marsden’s experiment?
A beam of alpha particles was aimed at gold foil and their passage through was detected. Some atoms were reflected, deflected or would pass straight through. This supported Rutherford’s atomic model.
What particles repel?
Positive and positive
What did the gold foil experiment show?
There’s much free space in the atom.
The nucleus has a positive charge.
The nucleus is large.
Which energy levels are filled first?
The lowest
2 8 8 2
What happens when atoms have full electron shells?
They are more stable. They are also less reactive as they don’t need to gain/lose electrons.
What happens when an atoms outer shell isn’t full?
It needs to react to maintain a stable, full outer shell.
How do you work out an elements electronic configuration?
It’s atomic number
What are electrons generally represented by on diagrams?
An X
