1. Atomic Structure and the Periodic Table
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45 Terms
What is an atom?
The smallest part of an element that can exist.
What is an element?
A substance made of only one type of atom.
What is a compound?
A substance made of two or more elements chemically combined in fixed proportions.
How are compounds separated?
By chemical reactions only.
What is a mixture?
Two or more substances not chemically combined.
Do substances in a mixture keep their properties?
Yes, their chemical properties stay the same.
Give two examples of physical separation techniques.
Filtration and crystallisation.
What did the plum pudding model suggest?
The atom is a ball of positive charge with electrons embedded in it.
What did the alpha scattering experiment show?
Mass is concentrated in a small, positively charged nucleus.
Who proposed that electrons orbit at specific distances?
Niels Bohr.
What did Chadwick discover?
The neutron.
What is the relative charge of a proton?
+1
What is the relative charge of a neutron?
0
What is the relative charge of an electron?
–1
What is the atomic number?
The number of protons in an atom.
What is the mass number?
The total number of protons and neutrons.
What are isotopes?
Atoms of the same element with different numbers of neutrons.
What is the radius of an atom?
Approximately 0.1 nanometres (1 × 10⁻¹⁰ m).
Where is most of the mass of an atom located?
In the nucleus.
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
Very small (≈ 0)
What is relative atomic mass?
The weighted average of the isotopes of an element, taking abundance into account.
How are electrons arranged in an atom?
In energy levels (shells) around the nucleus.
What is the electronic structure of sodium?
2,8,1
What does the periodic table show?
Elements arranged in order of increasing atomic number.
What do elements in the same group have in common?
Same number of electrons in the outer shell.
How did Mendeleev arrange the periodic table?
By atomic weight, leaving gaps for undiscovered elements.
Why was Mendeleev's table successful?
Elements later discovered matched his predictions.
Why are metals on the left of the periodic table?
They lose electrons to form positive ions.
Why are non-metals on the right of the periodic table?
They gain or share electrons.
What are Group 0 elements called?
Noble gases.
Why are noble gases unreactive?
They have full outer electron shells.
How does boiling point change down Group 0?
It increases.
What are Group 1 elements called?
Alkali metals.
How many outer electrons do Group 1 elements have?
One.
How does reactivity change down Group 1?
It increases.
What do Group 1 elements form with water?
A metal hydroxide and hydrogen gas.
What are Group 7 elements called?
Halogens.
How many outer electrons do Group 7 elements have?
Seven.
How does reactivity change down Group 7?
It decreases.
What is a halogen displacement reaction?
A more reactive halogen displaces a less reactive one from a salt solution.
Are halogens metals or non-metals?
Non-metals.
What is a diatomic molecule?
A molecule made of two atoms, e.g. Cl₂.