Unit-3 Atomic Structure
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Unit-3 Atomic Structure
Answer: Oxygen gains two electrons to form O2-, giving it a -2 charge.
Answer: 8 + 2 = 10 electrons in the oxide ion.
Answer: The atomic number of magnesium is 12, so it has 12 protons.
Answer: Neutrons = mass number - atomic number = 23 - 11 = 12.
Answer: Neutrons = 37 - 17 = 20.
Answer: Protium (hydrogen-1) has 1 proton and no neutrons.
Answer: All isotopes of hydrogen have 1 proton; tritium also has 2 neutrons.
Answer: Protons and neutrons have almost the entire mass of the atom; electrons are almost massless.
Answer: The proton and neutron have nearly equal masses of about 1 amu each.
Answer: Neutrons = 19 - 9 = 10.
Answer: The electron is about 1836 times lighter than a proton or neutron.
Answer: Argon has 18 electrons arranged as 2, 8, 8.
Answer: The configuration 2, 8, 1 corresponds to sodium (Z = 11).
Answer: Magnesium (Z = 12) has configuration 2, 8, 2, so it loses 2 electrons and has valency 2.
Answer: Only magnesium (Z = 12) has the configuration 2, 8, 2, giving three shells with two valence electrons.
Answer: Noble gases have complete outermost shells, so their valency is zero.
Answer: Phosphorus has 15 electrons arranged as 2, 8, 5.
Answer: Phosphorus has 5 valence electrons and needs 3 more to complete its octet, so its valency is 3.
Answer: A neutral atom has electrons equal to its atomic number, so sulfur has 16 electrons.
Answer: Potassium (Z = 19) has 19 electrons arranged as 2, 8, 8, 1.