1.1 A simple model of the atom & symbols
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What is an atom?
An atom is the smallest part of an element that can exist
What is an element?
An element is a substance of only one type of atom
How are the elements listed and approximately how many are there?
They are listed in the periodic table and there are approximately 100
Elements may combine through chemical reactions to form new products; what are these new substances called?
Compounds
What is a compound?
Two or more elements combined chemically in fixed proportions which can be represented by formulae
Do compounds have the same properties as their constituent elements?
No, they have different properties.
Describe the plum-pudding model
The atom is a ball of positive charge with negative electrons randomly placed in it.
Describe the Bohr / nuclear model and how it came about
The nuclear model suggests that electrons orbit the nucleus at specific distances (shells) – it came about after Rutherford’s alpha scattering experiment
Later experiments led to the discovery of smaller, positive particles in the nucleus; what are these particles called?
Protons
Who discovered the neutron? What year?
James Chadwick, 1932
Describe the structure of an atom
The atom has a small central nucleus (made up of protons and neutrons) around which there are electrons
What is the radius of an atom?
0.1 nm
What is the radius of a nucleus and what is it compared to that of the atom?
1 x 10^-14 m and 1/10000
What name is given to the number of protons in the nucleus?
Atomic number
Atoms of the same element have the same number of which particle in the nucleus?
Protons
Where is the majority of the mass of an atom?
The nucleus
How do you calculate the number of neutrons using mass number and atomic number?
Subtract the atomic number from the mass number
What is the mass number?
The total number of protons and neutrons
Atoms of the same element have the same number of which particle in the nucleus?
Protons
What is an isotope? Do isotopes of a certain element have the same chemical properties?
Atoms of the same element (same proton number) that have a different number of neutrons. They have the same chemical properties as they have the same electronic structure
Who discovered the electron? What year?
J.J. Thomson, 1897
Who proposed the plum pudding model?
J.J. Thomson
Who discovered the proton? What year?
Ernest Rutherford, 1917
Who proposed the nuclear model?
Ernest Rutherford