Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The Group 1 elements, known as the Alkali Metals, include Lithium (), Sodium (), Potassium (), Rubidium (), Cesium (), and Francium ().
All Group 1 atoms have exactly electron in their outermost shell, giving them a valency of .
Physical properties include being soft enough to cut with a knife, having low densities (the first three float on water), and having low melting and boiling points compared to other metals.
Reactivity increases down the group. This is because the atomic radius increases and there is more electron shielding, which weakens the electrostatic attraction between the positive nucleus and the outer , making it easier to lose.
Alkali metals react vigorously with water to produce a metal hydroxide (an alkaline solution) and hydrogen gas ().
They react with oxygen to form metal oxides () and with halogens to form ionic metal halides ().
📐Formulae
💡Examples
Problem 1:
Write the balanced chemical equation for the reaction between Sodium () and Water ().
Solution:
Explanation:
Sodium reacts with water to form Sodium Hydroxide and Hydrogen gas. The solution becomes alkaline, which would turn universal indicator purple or blue.
Problem 2:
Explain why Potassium (, atomic number ) is more reactive than Lithium (, atomic number ).
Solution:
Potassium has an electronic configuration of while Lithium is .
Explanation:
In Potassium, the valence electron is in the shell, which is further from the nucleus than Lithium's valence electron in the shell. Due to the increased distance and increased shielding from inner electrons, the nuclear attraction is weaker in Potassium, allowing it to lose its outer electron more easily.
Problem 3:
Calculate the number of neutrons in an atom of .
Solution:
Explanation:
The number of neutrons is calculated by subtracting the atomic number () from the mass number (). Sodium-23 has neutrons.