Unit 11: Patterns in periodic table Flashcards
What is density? State its SI unit and its formula.
Density refers to the amount of mass per unit volume. it comes from the particle structure (packing of particles).
Why do we use standardised units?
We use standardised units to bring uniformity in data and calculation.
What are the factors affecting density?
- mass
- Packing of particles (state of matter)
Temperature and pressure do not affect density directly.
Is conduction related to density?
Conduction of heat is NOT related to density.
How are elements grouped together in the periodic table?
The vertical columns of the periodic table are known as groups. Elements in a group have similar properties and same number of valence electrons.
Why does the size of the atom increase as you go down the group?
As we move down the group, the number of electrons increase and the distance of the outer electrons increase, leading to weaker forces of attraction/nuclear force, between the nucleus and the outer electrons.
What are group one elements?
Group one elements are elements which have 1 valence electron. They are Li (lithium), Na (sodium), K (potassium), Rb (Rubidium), Cs (caesium) and Fr (francium). There are known as alkaline metals.
What are the properties of group 1 elements?
- Soft
- Low density
- Low melting points
- Very reactive (as you go down reactivity increase - caesium catches fire at room temp)
- Melting and Boiling points decrease as you go down the group.
- Always form ionic compounds
- Form a cation with +1 charge.
Why are alkali metals highly reactive?
Alkali metals only have 1 electron in the outermost shell, which they lose easily to achieve octate.
Why does reactivity increase as you go down the group?
As atoms get larger, the distance of the outermost shell increases, so the attractive force weakens making it easier for the group 1 atom to lose its one electron, hence reactivity increases.
What is reactivity?
Reactivity refers to the ability to lose or gain electrons readily.
How do alkali metals react?
All reactions of alkali metals with water and hydrochloric acid are exothermic (releasing heat) and explosive in nature. As we move down the group, the more explosive the reaction.
How do group 1 metals react with water?
2M + 2H2O —-> 2MOH + H2 (general reaction)
For example -
2Li + 2H2O —–> 2LiOH + H2
Bases - alkali which have been dissolved in water
How do group 1 metals react with hydrochloric acid?
2M + 2HCl —-> 2MCl + H2. (general reaction)
For example -
2Na + 2HCl —-> 2NaCl + H2
What are group two elements?
Group two elements are elements which have 2 valence electrons. There are known as alkaline earth metals.
They are Be (barium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium) and Ra (Radium).
What are the properties of group 2 elements?
- Soft (as you go down, metals get softer)
- Low density
- Low melting points
- Very reactive (as you go down reactivity increase - caesium catches fire at room temp)
- Melting and Boiling points decrease as you go down the group.
- Form a cation with +2 charge.
How do group 2 metals react with water?
2M + 2H2O —-> 2M(OH)2 + H2 (general reaction)
For example -
2Ca + 2H2O —–> 2Ca(OH)2 + H2
Bases - alkali which have been dissolved in water
How do group 2 metals react with hydrochloric acid?
M + 2HCl —-> MCl2 + H2. (general reaction)
For example -
Mg + 2HCL —-> 2MgCl2 + H2
