3.1 The periodic Table Flashcards
(36 cards)
How are the elements arranged in a periodic table?
They are arranged in the order of increasing atomic numbers
What is a period on a periodic table?
The horizontal rows in the periodic table
What is a group on a periodic table?
The vertical columns
Who’s table is the modern one based off
Dmitri Mendeleev
Why did Mendeleev leave gaps in his table?
left gaps where no element at the time fitted the repeating patterns. properties of these were predicted
What is meant by periodicity?
The repeating trends in chemical and physical properties
What change happens across each period?
Elements change from metals to non metals
How can the electron configuration be written in short?
The noble gas before (period above)the element is used to abbreviate
E.g Li → 1s22s1 ; Li → [He] 2s1
What are the S block elements?
groups 1&2
What are the D block elements?
transition metals(middle part)
What are the P block elements?
groups 5-8
Define first ionisation energy
The energy required to remove 1 mole electron from 1 mol of gaseous atom to form one mole of gaseous 1+ ions
Write an equation for the first ionisation energy
X(g)→X+ (g) + e-
What are the factors that affect ionisation energy?
- Atomic radius(further away=less attraction)
- Nuclear charge
- Electron shielding or screening (more shells= more shielding)
How does electron shielding work?
Inner electron shells repel the outer electron shells. Shielding ‘blocks’ nuclear attraction reaching outer shells
What is the general trend for 1st ionisation across a period?
increase as
• across period protons increase but not shells so more nuclear attraction but similar shielding
Why does first ionisation energy decrease between group 2 to 3?
- group 2 outer electrons in s orbital,
* group 3 in P orbital so electrons are easier to remove as slightly further away
Why does first ionisation energy decrease between group 5 to 6?
group 5 electrons in P orbital are single electrons group 6 are spin paired, with some repulsion. so they are slightly easier to remove
Does first ionisation increase or decrease between the end of one period and the start of next? Why
Decrease
• There is increase in atomic radius
• Increase in electron shielding (new shell added)
Does first ionisation increase or decrease down a group?
Why?
Decrease
• Shielding increases → weaker attraction
• Atomic radius increases → distance between the outer electrons and nucleus increases → weaker attraction
• Increase in number of protons is outweighed by increase in distance and shielding
What are the properties of giant metallic lattices? (4)
- High melting and boiling point
- Good electrical conductors
- Malleability(can be moulded)
- Ductility (can be stretched)
Describe the structure, forces and bonding in every element across period 2
- Li & Be → giant metallic ; strong attraction between cations and delocalised electrons ; metallic bonding
- B & C → giant covalent ; strong forces between atoms covalent
- N2 ,O2 ,F2 ,Ne → simple molecular ; weak intermolecular forces, covalent bonding
Describe the structure, forces and bonding in every element across period 3
- Na, Mg, Al → giant metallic lattice, strong attraction between cations and delocalised electrons, metallic bonding
- Si → giant covalent lattice, strong forces between atoms, covalent bonding
- P4 , S8 , Cl2 , Ar → simple molecular, weak intermolecular forces ,covalent bonding
Group 2 Properties
• high-ish melting & Boiling point
• increasing atomic radii down group
• increasing reactivity with water down group
Increasing solubility
• 2+ oxidation states in compounds (outer shell 2 electrons
