Chemistry (4th Edition)

Published by McGraw-Hill Publishing Company
ISBN 10: 0078021529
ISBN 13: 978-0-07802-152-7

Chapter 2 - Questions and Problems - Page 76: 2.16

Answer

Helium - 4 isotope has 2 protons and 2 neutrons. Helium - 4 isotope has 2 protons and 2 neutrons. Its atomic number is 2 (protons).. All the isotopes of an element have the same atomic number (same number of protons), so, all have 2 protons. The number 4 that identifies the helium - 4 isotope is the mass number so, helium-4 isotope has 2 protons and 2 neutrons. The atomic number enables us to deduce the number of electrons in an atom because the atoms are neutral, which means that the positive and negative charge are equal. Given that the magnitude of the charge of electrons and protons are equal but the sign is opposed (protons are positive and electrons are negative) the number of electrons in the atom equals the number of protons and therefore, the atomic number is also the number of electrons of the atom for a neutral atom.

Work Step by Step

Helium - 4 isotope has 2 protons and 2 neutrons. Its atomic number is 2 (protons).. All the isotopes of an element have the same atomic number (same number of protons), so, all have 2 protons. The number 4 that identifies the helium - 4 isotope is the mass number so, helium-4 isotope has 2 protons and 2 neutrons. The atomic number enables us to deduce the number of electrons in an atom because the atoms are neutral, which means that the positive and negative charge are equal. Given that the magnitude of the charge of electrons and protons are equal but the sign is opposed (protons are positive and electrons are negative) the number of electrons in the atom equals the number of protons and therefore, the atomic number is also the number of electrons of the atom for a neutral atom.
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