1.1 Atomic structure and atomic table
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85 Terms
What is an atom?
The smallest part of an element that can exist
What do atoms make up?
All substances
What does a chemical symbol represent?
An atom of an element
Give an example of a chemical symbol.
Na represents sodium
What is a compound?
A substance formed from two or more elements chemically combined in fixed proportions
What happens in a chemical reaction?
New substances are formed, often with an energy change
How can compounds be separated?
Only by chemical reactions
Give an example of a compound.
HCl (1 hydrogen atom and 1 chlorine atom)
What is a mixture?
Two or more substances not chemically combined
What happens to chemical properties in a mixture?
They remain unchanged
How are mixtures separated?
Physical processes (e.g. filtration, distillation, chromatography)
Do mixtures involve chemical reactions when separated?
No
What was the earliest model of the atom?
A tiny indivisible solid sphere
What is the plum pudding model?
A ball of positive charge with electrons embedded in it
What did the alpha scattering experiment show?
The atom has a small, dense, positively charged nucleus
Why were some alpha particles deflected?
They were repelled by the positive nucleus
Who suggested electrons orbit in shells?
Bohr
Who discovered protons?
Rutherford (concept developed after experiments)
Who discovered neutrons?
James Chadwick
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 is the charge of a proton?
+1
What is the charge of a neutron?
0
What is the charge of an electron?
-1
Why is an atom neutral?
Number of protons = number of electrons
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 the size of an atom?
About 0.1 nm
Where is most of the mass in an atom?
In the nucleus
What are isotopes?
Atoms of the same element with different numbers of neutrons
What is relative atomic mass?
A weighted average of isotopes based on abundance
How do you calculate relative atomic mass?
((mass × abundance) + (mass × abundance)) ÷ 100
Where are electrons found in an atom?
In energy levels (shells) around the nucleus
What is electronic structure?
The arrangement of electrons in shells
Give the electronic structure of sodium.
2,8,1
Where do electrons fill first?
The lowest energy level closest to the nucleus
What are transition metals?
Metals in the centre of the periodic table
How do transition metals compare to group 1 metals?
Harder, stronger, higher melting points, less reactive
What are typical properties of transition metals?
Form coloured compounds, have variable charges, act as catalysts
Why are transition metals good catalysts?
They can form ions with different charges easily
What is the periodic table arranged by?
Atomic (proton) number
What is a group?
A column of elements with similar properties
Why do elements in the same group have similar properties?
Same number of outer shell electrons
Who proposed the law of octaves?
Newlands
Why did Newlands' table fail?
Pattern broke down after calcium
Who developed the modern periodic table?
Mendeleev
What was Mendeleev’s key idea?
Left gaps for undiscovered elements
What are metals?
Elements that form positive ions
Where are metals found in the periodic table?
Left and bottom
What are non-metals?
Elements that do not form positive ions
Where are non-metals found?
Right and top
What are Group 1 elements called?
Alkali metals
How do Group 1 metals react with water?
Form alkaline solution and hydrogen
How does reactivity change down Group 1?
Increases
Why does reactivity increase down Group 1?
Outer electron is further from nucleus and easier to lose
What are Group 7 elements called?
Halogens
What is the charge of halide ions?
-1
How do halogens react with metals?
Form ionic compounds
How do halogens react with non-metals?
Form covalent compounds
How does reactivity change down Group 7?
Decreases
Why does reactivity decrease down Group 7?
Increased shielding reduces attraction for electrons
What is displacement in halogens?
A more reactive halogen displaces a less reactive one
Give an example of displacement.
Chlorine + potassium bromide → potassium chloride + bromine
What are Group 0 elements called?
Noble gases
Why are noble gases unreactive?
They have full outer shells
How do boiling points change down Group 0?
Increase