(FAMILIES OF ELEMENTS) PERIODIC TRENDS Lesson Note
LEARNING OBJECTIVES:
This SS2 Chemistry lesson note covers (FAMILIES OF ELEMENTS) PERIODIC TRENDS for First Term, Week 3.
Lesson Note
LEARNING OBJECTIVES:
By end of lesson, students should be able to:
1. Define families of elements
2. State why elements in same group have similar properties
3. List 5 period trend
4. State the trend of a period.
A. PERIOD PROPERTIES AND THEIR VARIATION IN PERIODS AND GROUPS
Periodic properties means the properties which recur at regular intervals in the periodic table. This phenomenon is called Periodicity.
ATOMIC SIZE OR ATOMIC RADIUS : Atomic size is the distance between the centre of the nucleus of an atom and its outermost shell.
Variation: The atomic size of element decreases in a period from left to right and increases from top to bottom in the group.
IONIZATION ENERGY : Ionization potential of an element is the amount of energy required to remove the most loosely bound electron from the outermost shell of an isolated gaseous atom of that element.
Variation: the Ionization potential in a period increases on moving from left or right and decreases on moving from top to bottom on the group.
ELECTRON AFFINITY: Electron affinity is the amount of energy released when an isolated gaseous neutral atom accepts an electron to form an anion
Variation: The electron affinity increases in a period as we move from left to right and decreases in a group when we move from top to bottom.
ELECTRONEGATIVITY: It is the tendency of an atom in a molecules to attract the shared pair of electrons toward itself in a molecule Or is the ability of an atom in a molecule to attract electron.
Variation: Electronegativity increases across period on moving from left to right and decreases down the group.
ELECTROPOSITIVITY: It is the tendency of an atom to lose one or more electrons to acquire a stable electronic configuration.
Variation: The electropositivity in a period decreases on moving from left to right and increases in a group on moving from top to bottom.
Evaluation
OBJECTIVE QUESTION
1. Vertical columns in the periodic table are called:
A) Periods
B) Groups/Families
C) Blocks
D) Series
2. Elements in the same family have similar chemical properties because they have:
A) Same atomic number
B) Same number of shells
C) Same number of valence electrons
D) Same mass number
3. Which group is known as Alkali metals?
A) Group 2 B) Group 1 C) Group 7 D) Group 0
4. The most reactive element in Group 1 is:
A) Lithium
B) Sodium
C) Potassium
D) Francium
5. Which element reacts violently with cold water to produce hydrogen gas?
A) Calcium
B) Sodium
C) Magnesium
D) Argon
6. Halogens have a valency of:
A) 1+
B) 2+
C) 1-
D) 2-
7. Which of the following exists as a liquid at room temperature?
A) Fluorine
B) Chlorine
C) Bromine
D) Iodine
8. Noble gases are unreactive because:
A) They have 7 valence electrons
B) Their outer shell is completely filled with electrons (octet)
C) They are metals
D) They have high density
9. Which of these is a property of transition metals?
A) Low melting point
B) Form only white compounds
C) Have variable oxidation states and form coloured compounds
D) Very soft
10. As you go DOWN Group 1, the reactivity:
A) Decreases
B) Increases
C) Remains same
D) Becomes zero
Theory Questions
QUESTION 1:
a) Define families of elements and state why elements in same group show similar chemical behaviour.
b) List the members of the following families: i) Alkali metals ii) Halogens iii) Noble gases
c) State 2 properties and 1 use of each: Alkali metals and Halogen
QUESTION 2:
a) Differentiate between Alkaline earth metals and Transition metals under: i) Position in periodic table ii) Valency iii) Nature of compounds formed.
b) The electronic configuration of an element is 2,8,8,2. Identify the element, its group, family, and write equation of its reaction with cold water.