How many periods and groups are there in the modern periodic table?
- A.8 periods and 7 groups
- B.18 periods and 7 groups
- C.7 periods and 18 groups
- D.7 periods and 8 groups
Correct answer
Explanation
The correct answer is C, 7 periods and 18 groups. The modern periodic table has seven horizontal rows, called periods, and eighteen vertical columns, called groups. The first period holds only two elements, the second and third hold eight each, the fourth and fifth hold eighteen each and the sixth holds thirty-two, while the lanthanides and actinides are shown in two separate rows below. Option A is wrong because it reverses the two counts. Option B is wrong because eighteen is the number of groups, not of periods. Option D is wrong because eight groups belonged to Mendeleev's older table, which had eight vertical columns; the eighteen-group form came with the long form of the modern table, in which elements of a group share the same number of outermost electrons. A useful check is that seven is always the smaller of the two numbers, because the table is wider than it is tall.
Read the full article: Atomic Structure and Periodic Table: Models and Trends
Practice Questions
View allWho coined the word 'atom'?
- A.Democritus
- B.Thomson
- C.E Rutherford
- D.John Dalton
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The Greek philosopher Democritus, working in the fifth century before the common era, argued that matter could be divided only up to a limit, and he called that smallest indivisible particle atomos, from which the word atom comes.
Read the full explanation →Who among the following discovered the neutrons?
- A.J. Chadwick
- B.E. Goldstein
- C.Neils Bohr
- D.Ernest Rutherford
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James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles and showing that the radiation produced consisted of neutral particles of nearly the same mass as the proton.
Read the full explanation →Rutherford's alpha-particle scattering experiment on a thin gold foil led to which conclusion?
- A.Electrons are embedded in a sphere of positive charge
- B.The atom is indivisible
- C.Electrons revolve in fixed permitted orbits
- D.Almost all the mass and the positive charge lie in a tiny nucleus
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Most alpha particles passed straight through the foil, a few were deflected through small angles and about one in twenty thousand bounced back.
Read the full explanation →The maximum number of electrons that can be accommodated in the M shell is:
- A.8
- B.2
- C.18
- D.32
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The capacity of a shell is given by the formula 2n squared, where n is the number of the shell counted outward from the nucleus.
Read the full explanation →Alkali metals are assigned which group in the Modern Periodic Table?
- A.Second group
- B.Eighteenth group
- C.Third group
- D.First group
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The alkali metals are lithium, sodium, potassium, rubidium, caesium and francium. Each has a single electron in its outermost shell, loses it readily to form a positive ion, and therefore stands in group 1 of the modern periodic table.
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