Atomic Structure and the Periodic TableCambridge IGCSE Chemistry: Flashcards

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Describe the structure of an atom.

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Describe the structure of an atom.: An atom consists of a central nucleus containing protons and neutrons, surrounded by electrons in shells (electron orbitals) arranged around the nucleus.
What is the relative charge of a proton?: +1 (or positive charge)
What is the relative charge of a neutron?: 0 (neutral; no charge)
What is the relative charge of an electron?: -1 (or negative charge)
State the relative mass of a proton and a neutron.: Both proton and neutron have a relative mass of 1 (approximately equal mass)
What is the relative mass of an electron?: Approximately 1/1836 (negligible; usually taken as 0)
Define proton number (atomic number).: The number of protons in the nucleus of an atom. This defines the element and determines its atomic number.
Define mass number (nucleon number).: The total number of protons and neutrons in the nucleus of an atom.
How do you calculate the number of neutrons in an atom?: Mass number minus proton number (nucleon number – atomic number)
What is the electronic configuration of oxygen (proton number 8)?: 2,6 (2 electrons in the first shell, 6 electrons in the second shell)
What is the electronic configuration of calcium (proton number 20)?: 2,8,8,2 (2 electrons in first shell, 8 in second, 8 in third, 2 in fourth)
Why do noble gases (Group VIII) have a full outer electron shell?: Noble gases have completely filled valence (outer) electron shells, making them very stable and unreactive. They do not need to gain, lose, or share electrons.
State the relationship between group number and outer shell electrons (Groups I–VII).: The number of electrons in the outer shell equals the group number. For example, Group IV elements have 4 outer electrons.
What is the relationship between period number and the number of occupied electron shells?: The number of occupied electron shells equals the period number. For example, Period 3 elements have 3 electron shells.
Determine the electronic configuration of a chloride ion (Cl⁻) with proton number 17.: 2,8,8 (chloride ion has gained one electron; it has 18 electrons total, giving it a full outer shell like argon)