Atoms Flashcards
(26 cards)
Explain John Daltons theory
He thought atoms were small solid spheres and that different spheres made up the different elements
Explain JJ Thomson’s theory
His theory was known as “plum pudding model”
he said that the atom was mostly positive with small negatively charged particles - electrons
Explain Rutherford’s theory
He did the gold foil experiment with his students Geiger and Marsden with alpha particles and discovered that there was a ting positively charged nucleus in the atom with negative electrons floating around
Gold foil experiment
They fired positively charged alpha particles at an thin gold sheet. Most went right through. Some were deflected (more than expected) and some were deflected backwards
Explain Bohr model
his model said electrons can only exist in fixed orbits or shells. Each shell has a fixed energy. with a nucleus in the middle.
What does the smaller number of an element mean on the periodic table ?
The smaller number is the atomic number
The number of protons
How do we find the number of electrons ?
It will always be the same as the number of protons
How do we find the number of neutrons ?
mass number - atomic number
What does the mass number tell us ?
number of protons + number of neurons
Most of the mass is centered in the nueclus but the electrons shells take at lot of space
What is the relative mass of protons ?
1
What is the relative mass of electrons ?
0.0005
What is the relative mass of a neutron
1
What is the relative charge of protons ?
+1
What is the relative charge of neutron ?
0
What is the relative charge of electron ?
-1
Why is the number of protons and electrons same ?
Because the positive protons and negative electrons cancel out making the atom electrically neutral
They will always balance out
What is mass number ?
The number of protons and neutrons.
What do all atoms of the same element have ?
The same number of protons
What is an isotope ?
Isotopes are different forms of the same elements, that have the same number of protons, but a different number of neutrons.
How to calculate relative atomic mass ?
Mass number x the percentage (abundance) + Mass number x the percentage (abundance) of isotope 2 = x
x÷ both abundance added
Explain why isotopes may lead to mass numbers not being whole numbers
They are a weighted average of the mass number of the different isotopes
What is abundance ?
How common each isotope is
What is a nuclide?
A nuclide is a specific nucleus that contains a certain number of protons and neutrons
What do all atoms of the same element have
The same atomic number / the same number of protons
