Periodic trends Flashcards
What is electronegativity?
The ability of an atom to attract bonding electrons
What are three factors that influence electronegativity?
- atomic radius
- number of shells/shielding
- nuclear charge
Does electronegativity increase or decrease across a period?
Increase.
Does electronegativity increase or decrease down a group?
Decrease.
Why does electronegativity decrease down a group?
More shells= more shielding and atomic radius increases (outer shell further from nucleus).
Why does electronegativity increase across a period?
Nuclear charge increases, atomic radius decreases and therefore the attraction of electrons increases. Same shell= similar shielding. More protons are being added which increases charge of nucleus and pulls electrons closer together.
How does bonding change across a period?
Bonding changes from metallic to giant covalent to simple covalent.
What are the bonds/forces like in metallic bonds?
Strong forces between metal cations and delocalised electrons (electrostatic)
What are the bonds/forces like in giant covalent bonds?
Strong bonds between atoms.
What are the bonds/forces like in simple molecular covalent bonds?
Weak intermolecular forces between molecules (London forces)
What are the melting points like in simple molecular covalent bonds?
Low melting points
What are the melting points like in giant covalent and metallic bonds?
High melting points.
What happens to the melting points between metallic/giant covalent bonds and simple molecular covalent bonds?
Huge drop in melting points as bonding goes from giant molecules to small molecules
What happens across a period in metals? (4 points)
-Strength of metallic bond increases
-Bonds harder to break
-Melting point increases
-Bonds get stronger because charge on metal cation increases (+1 in group 1, +2 in group 2)
What happens down a group in metals? (4 points)
-Strength of metallic bond decreases
-Bonds easier to break
-Melting point decreases
-Bonds get weaker because atoms get bigger and the attractions because metal cations and delocalised electrons become weaker
What happens down a group in non-metals? (3 points)
-Atoms/molecules held together by London forces
-Strength of intermolecular forces increases down a group as size of atom increases
-Melting point increases
What are cations?
Smaller than atoms because they have lost electrons.
What are anions?
Larger than atoms because they have gained electrons.
What is first ionisation energy?
Minimum energy needed to remove an electron from an atom (as a a gas).
The higher the first ionisation energy= ?
Harder it will be for the element to lose an electron and become a cation.
What happens in the first ionisation energy down a group?
Decreases because atomic radius increases therefore there are more shells so attraction of electron decreases- easier to remove electron because less attraction.
What happens in the first ionisation energy across a period?
Increases because nuclear charge increases, therefore attraction increases. Same shell: similar shielding.
