Atomic Structure & The Periodic Table
Atoms are the building blocks of all matter, consisting of a small, positively charged central nucleus containing protons and neutrons surrounded by electrons arranged in energy levels (shells). The modern Periodic Table orders elements by atomic number (proton number) so that elements in the same vertical group have the same number of outer-shell electrons and similar chemical properties.
- Proton
- A subatomic particle found in the nucleus of an atom with a relative charge of +1 and relative mass of 1.
- Neutron
- A subatomic particle found in the nucleus with no charge and a relative mass of 1.
- Electron
- A negatively charged subatomic particle that orbits the nucleus in shells, with a relative mass of almost zero.
Atomic Shell Configuration & Subatomic Particle Explorer
Sodium (Na), Group 1 Alkali Metal
Protons (= Atomic Number): 11 (charge +1, mass 1)
Electrons (in neutral atom): 11 (charge −1, mass ~0)
Neutrons (Mass − Atomic Number): 23 − 11 = 12 (charge 0, mass 1)
Electronic Configuration: 2.8.1
Key Concepts & Exam Definitions (5)
- Proton
- A subatomic particle found in the nucleus of an atom with a relative charge of +1 and relative mass of 1.
- Neutron
- A subatomic particle found in the nucleus with no charge and a relative mass of 1.
- Electron
- A negatively charged subatomic particle that orbits the nucleus in shells, with a relative mass of almost zero.
- Isotope
- Atoms of the same element with the same number of protons but a different number of neutrons.
- Group
- A vertical column in the periodic table containing elements with similar chemical properties.
Quick-Fire Flashcards (5)
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What is the relative charge of an electron?
Where is most of the mass of an atom concentrated?
What do elements in the same group have in common?
Who designed the modern periodic table?
What are Group 1 elements called?
Exam-Style Questions & Mark Schemes (3)
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- Q1
An atom of sodium has an atomic number of 11 and a mass number of 23. Calculate the number of protons, neutrons, and electrons.
Click “Check Mark Scheme” to compare your answer, Protons = 11, Electrons = 11, Neutrons = 23 - 11 = 12.
- Q2
Explain why isotopes of an element have the same chemical properties.
Click “Check Mark Scheme” to compare your answer, They have the same number of electrons in their outer shell, which determines chemical behaviour.
- Q3
Describe the trend in reactivity as you go down Group 7 (Halogens).
Click “Check Mark Scheme” to compare your answer, Reactivity decreases down the group because the outer shell is further from the nucleus, making it harder to gain an electron.
Common Exam Questions (3)
What is the structure of an atom?
An atom consists of a tiny, dense central nucleus containing positively charged protons and neutral neutrons, surrounded by negatively charged electrons orbiting in shells (energy levels) at relatively large distances from the nucleus.
What is atomic number and mass number?
The atomic number (proton number) is the number of protons in the nucleus of an atom, which defines the element. The mass number is the total number of protons and neutrons combined in the atom's nucleus.
How is the periodic table arranged?
The Periodic Table arranges elements in order of increasing atomic number in horizontal rows called periods and vertical columns called groups; elements in the same group have the same number of electrons in their outer shell and react in similar ways.
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