1.6 - The Periodic Table Flashcards
- Periodic Table Trends, Group 1,2 and 7 chemistry (69 cards)
What is the term for rows in the periodic table?
Periods
What is the term for columns in the periodic table?
Groups
What trend is observed across a period?
Ionisation energy
What trends are observed down a group?
Physical properties
Same outer electron configuration
What is first ionisation energy?
The first ionisation energy of an element is the energy required to remove one electron from each atom in a mole of gaseous atoms.
Which group are the best reducing agents?
Trend in reducing ability in this group?
Group 1 - Group 1 elements have better reducing ability down the group
Caesium = most electropositive
What Group is the best oxidising agent?
What is the trend in oxidising ability in this group?
Group 7 - Group 7 elements are better reducing agents further up the group.
What is unique about d-Block elements?
They often exist in more than one oxidation state, so can both donate and accept electrons
Define Electronegativity
The measure of an atom’s ability to attract a bonding electron in a covalent bond.
What is the most electronegative element and what is it given on the Pauling Scale?
Fluorine - 4.0
Are elements more or less electronegative across a period - Why?
Elements are more electronegative across a period -
- There is an increase in nuclear charge across the period.
- However, bonding electrons are always shielded by the same inner electrons.
- So nuclear charge increases but shielding effect and distance from the nuclear doesn’t.
- This creates greater attraction between the nucleus and the bonding pair.
-This means the element is more able to attract a bonding electron and therefore is more electronegative.
Are elements more or less electronegative down a Group?
Elements become less electronegative down a group -
- There is an increase in shielding effect from inner electrons and distance from the nucleus.
-This outweighs the increase in nuclear charge, therefore attraction between the bonding electrons and the nucleus decreases.
- This means the element is less able to attract a bonding electron, therefore it is less electronegative.
What three factors are there when considering the electronegativity of an element?
-Nuclear charge
-Distance between the bond and nucleus
-Shielding effect caused by inner electrons
Does first ionisation energy increase or decrease across a period?
Generally it increases -
- Increase in nuclear charge
- Electrons are being added to the same shell/ energy level
-Therefore little increased shielding effect
-Therefore, a greater attraction between the nucleus and outer electrons
- Atoms become smaller
Anomalies in first ionisation energy?
Groups 2-3
Groups 5-6
Why is there anomaly in F.I.E trends between Group 2-3?
There is a decrease in I.E between Groups 2 and 3.
- In Group 3 the outer electron is in a new subshell of a slightly higher energy level.
-The inner s-subshell shields the outer electron reducing the I.E required.
Why is there an anomaly in F.I.E between Groups 5-6?
There is a decrease in F.I.E between Group 5-6.
- In Group 5 all of the outer electronsa re in their own orbitals.
In Group 6, the additional electrons shares an orbital.
-The repulsion between electrons in the same orbital makes it easier to remove, therefore a decrease in I.E
Why does ionisation energy decrease down a group?
The increase distance from the nucleus + increase shielding effect from inner electrons outweighs the increase in nuclear charge, therefore easier to remove, therefore lower I.E.
What factors does melting point depend on?
Structure and bonding present
Melting point trend in Group 1?
melting point decreases down the group -
Metallic bonding becomes weaker
-Metallic bonding depends on the attraction of the nucleus to the delocalised valence electrons.
-This becomes weaker upon descending Group 1 as the atoms become bigger and so the valence electrons become further away from the nucleus.
Bonding Trends Across Period 3?
Na, Mg, Al, Si, P, S, Cl, Ar
- Na, Mg and Al - Metallic bonding present therefore high melting point
Melting point increases in the metals as there is a stronger metallic bonds
Greater charge and more delocalised electrons per atom. - Silicon is a giant covalent structure, therefore very high melting point.
-P, S and Cl are all simple covalent structures. Weak intermolecular Van der Waals forces result in a low melting point.
-Argon is atomic therefore it is held together by very weak dipole-induced dipole-induced forces, hence the lowest emlting point.
Reactivity in Group 1 and 2 -
Reactivity increases down both groups
Atoms get bigger therefore the distance from nucleus increases.
The increase in distance + increased shielding effect from inner electrons outweighs the increase in nuclear charge.
Therefore it easier to form the cation, less energy required.
Difference in reactivity between Group 1 and 2
Group 2 is less reactive.
It takes more energy to remove two electrons
Group 2 elements are smaller, therefore increased attraction.
How do you test for cations?
Flame test
