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Questions and Answers
Which trend is observed in the physical properties of alkali metals as you move down the group?
Which of the following describes a chemical property of alkali metals?
How does the reactivity of alkali metals change as you go down the group?
When an alkali metal reacts with water, what type of product is typically formed?
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Which balanced equation correctly represents the reaction of sodium with water?
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Study Notes
Trends in Physical Properties
- Alkali metals (Group 1 elements: Li, Na, K, Rb, Cs, Fr) are characterized by low densities, with the first three (Li, Na, K) being less dense than water.
- They exhibit a shiny, metallic luster when freshly cut, but tarnish rapidly due to oxidation.
- Melting and boiling points decrease as atomic number increases, resulting in lower values for heavier metals.
- Alkali metals are highly malleable and ductile, easily deformed under pressure.
Chemical Properties
- Alkali metals are highly reactive, particularly with water, resulting in the formation of hydroxides and hydrogen gas.
- Reactivity increases down the group; Li reacts less violently, while Cs reacts explosively with water.
- They readily lose one electron to form +1 cations, making them strong reducing agents.
- They can react with halogens to form ionic salts, exemplified by reactions with chlorine to produce metal chlorides.
Trends in Reactivity
- Reactivity increases down the group as the outer electron is further from the nucleus, making it easier to lose.
- The shielding effect increases with more electron shells, leading to lower ionization energies, thus enhancing reactivity.
- Lithium shows the least reactivity, while francium is the most reactive but is highly radioactive and rare.
Balanced Equations for Reactions
- Reaction with water:
( 2 \text{M} + 2 \text{H}_2\text{O} \rightarrow 2 \text{MOH} + \text{H}_2 ) (where M represents an alkali metal) - Reaction with halogens:
( 2 \text{M} + \text{X}_2 \rightarrow 2 \text{MX} ) (where X is a halogen, e.g., Cl, Br) - Combustion in air:
( 4 \text{M} + \text{O}_2 \rightarrow 2 \text{M}_2\text{O} )
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Description
Test your knowledge on the physical and chemical properties of alkali metals. This quiz covers trends in reactivity and includes balanced equations for their reactions. Assess your understanding of this essential group in the periodic table.
