Unit-3 Atomic Structure
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Unit-3 Atomic Structure
Answer: Protium (hydrogen-1) is the most abundant isotope, making up more than 99% of natural hydrogen.
Answer: Deuterium (hydrogen-2) has 1 proton and 1 neutron.
Answer: Tritium has mass number 3 and 1 proton, so neutrons = 3 - 1 = 2.
Answer: C-14 is radioactive and its decay is used to estimate the age of ancient materials.
Answer: Average = (0.75 x 35) + (0.25 x 37) = 26.25 + 9.25 = 35.5 amu.
Answer: Oxygen has 8 electrons filled as 2 in K and 6 in L, written 2, 6.
Answer: Sodium's 11 electrons fill as 2, 8, 1 across the K, L and M shells.
Answer: Sodium's configuration 2, 8, 1 shows it has three shells: K, L and M.
Answer: Chlorine has 17 electrons arranged as 2, 8, 7 in the K, L and M shells.
Answer: Calcium's 20 electrons fill as 2, 8, 8, 2 in the K, L, M and N shells.
Answer: Sodium has one electron in its outermost shell and loses it, so its valency is 1.
Answer: Oxygen has 6 valence electrons and gains 2 more to complete its octet, so its valency is 2.
Answer: Nitrogen has 5 valence electrons and needs 3 more to complete its octet, so its valency is 3.
Answer: Carbon has 4 valence electrons, so its valency is 4.
Answer: Chlorine needs only one electron to complete its octet, so its valency is 1.
Answer: Valency is the combining capacity of an atom, determined by its valence electrons.
Answer: Losing electrons gives the atom a positive charge, forming a cation.
Answer: Gaining electrons gives the atom a negative charge, forming an anion.
Answer: Sodium loses one electron to form Na+, which carries a +1 charge.
Answer: 11 - 1 = 10 electrons remain after sodium loses one electron.