Periodic table and periodicity of properties
Question 1: Define following terms:
Periodic table; periodic law; periods of elements; groups of elements; short periods and long periods.
Answer
Periodic table: A table that shows a systematic arrangement of elements is called periodic table.
Periodic law: According to this law, the elements are arranged with increasing order of the atomic numbers their properties are repeated in periodic manners.
Periods: The horizontal rows of periodic table are known as periods.
Short periods: First three periods are called short periods.
Long periods: Periods number 4, 5, 6 and 7 are called Long periods.
Groups: The vertical columns of periodic tables are known as groups. All elements are divided into two groups.
Question 2: Differentiate between normal a Representative elements and transition elements
Answer.
Normal or Representative elements: Group A elements are called Normal or representative elements.
Transition elements: Group B elements are called transition elements.
Question 3: What are alkali metals, alkaline earth metals, halogens and noble gases?
Alkalie metals: Group IA elements are called alkali metals.
Alkaline earth metals: Group IIA elements are called alkaline earth metals.
Halogens: Group VIIA elements are called halogens.
Noble gases: group VIIIA elements are called noble gases.
Question 4: Differentiate between s-block and p- block elements.
Answer
s-block elements: Elements of IA and IIA groups are called a-block elements.
p-lock elements: The elements of III-A group to VIIIA elements are called p-Block elements.
Question 5: what is shielding effect? give its friend in the periodic table.
Answer.
Shielding effect: The decrease in force of attraction between nucleus and the valence electrons due to to inner shell electron is called shielding effect.
Trend in Periodic Table
Question 6: What is atomic size? Describe its trend in periodic table with reason.
Answer.
Atomic size: Average distance between nucleus of an atom and its valence shell is called atomic size
Trend in Periodic Table
In period:
Atomic size decreases from left to right in the period.
Reason: As we move from left to right across the period, valence shall remains the same. At the same time, the positive charge of nucleus goes on increasing. As a result force of attraction between nucleus and valence electron also increases. Therefore, atomic size decreases.
In group:
Atomic size increases from top to bottom of a group.
Reason: Size of atom is determined from size of valence shell. As we move from top to bottom along a group, each atom has an additional shell of electrons. This increases size of valence shell. Hence, size of atoms also increases.
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