Atomic Structure and the Periodic Table Flashcards
(33 cards)
What’s an atom?
The smallest part of an element that can exist.
What’s an atom of an element represented by?
A chemical symbol
eg: O represents Oxygen
Where are elements shown?
The Periodic Table
What do chemical reactions always involve?
The formation of one or more new substances and often a detectable energy change.
What do compounds contain?
Two or more elements chemically combined in fixed proportions.
Can compounds be separated into elements?
Yes, but only by chemical reactions.
What does a mixture contain?
Two or more elements or compounds which are not chemically combined together.
Note: The chemical properties of each substance in the mixture are unchanged.
Can mixtures be separated?
Yes; by physical processes such as: filtration, crystallisation, simple distillation, fractional distillation and chromatography.
Those processes don’t involve chemical reactions and no new substances are made.
What were atoms thought to be before the discovery of the electron?
Tiny spheres which couldn’t be divided.
What’s the plum pudding model of an atom?
It suggests that the atom is a ball of positive charge with negative electrons embedded in it.
What did the alpha particle scattering experiment tell us?
It led us to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. This model went on to replace the plum pudding model.
How was the nuclear model adapted by Niels Bohr?
He suggested that electrons orbit the nucleus at specific distances.
Just after Niels Bohr’s adaptation what did later experiments show?
They gave the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. Those particles were given the name “protons”.
Who came up with the idea that there are neutrons in the nucleus?
James Chadwick
What’s the relative charge of a proton?
+1
What’s the relative charge of a neutron?
0
What’s the relative charge of an electron?
-1
In an atom what’s equal in the nucleus?
The amount of protons and electrons which is therefore why the nucleus is neutral.
Atoms have…
No overall electrical charge
What’s an elements atomic number?
The number of protons in an atom.
Do atoms of different elements have different numbers of protons?
Yes
What’s an atom’s radius?
0.1nm
Where is almost all the mass of an atom found?
In the nucleus
What’s the relative mass of a proton?
1
