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Questions and Answers
What trend is observed in the physical properties of alkali metals as you move down the group?
Which chemical property is characteristic of alkali metals?
How does the reactivity of alkali metals change as you go down the group?
Which balanced equation correctly represents the reaction of sodium with water?
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Which alkali metal is expected to be the most reactive?
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What happens to the melting points of alkali metals as you move down the group?
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Which of the following statements about the solubility of alkali metal hydroxides in water is correct?
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When lithium reacts with chlorine, which products are expected?
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How does the reactivity of alkali metals compare to that of alkaline earth metals?
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Which balanced equation represents the reaction of potassium with water?
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Study Notes
Trends in Physical Properties of Alkali Metals
- Alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).
- Physical properties vary with increasing atomic number: melting and boiling points decrease.
- Alkali metals are soft, with a characteristic silvery luster, becoming more malleable as you move down the group.
- Density generally increases down the group, with lithium being less dense than water.
- Higher reactivity accompanies lower ionization energies, which decrease as you move down the group.
Chemical Properties of Alkali Metals
- Alkali metals react vigorously with water to produce hydroxides and hydrogen gas, releasing heat.
- Reactivity increases down the group; lithium reacts moderately, while cesium is explosively reactive.
- Alkali metals form ionic compounds with halogens; the halide salts are typically soluble in water.
- Reactions with oxygen form oxides (Li2O), peroxides (Na2O2), or superoxides (KO2), depending on the metal.
Trends in Reactivity of Alkali Metals
- Reactivity increases down the group due to lower ionization energies, making it easier to lose the outermost electron.
- Cesium is the most reactive, while lithium is the least reactive.
- Alkali metals must be stored under oil or inert gas to prevent reactions with moisture and air.
Writing Balanced Equations for Reactions of Alkali Metals
- Example reaction with water:
- 2Na + 2H2O → 2NaOH + H2↑
- Example reaction with halogens:
- 2K + Cl2 → 2KCl
- Example reaction with oxygen (for sodium):
- 4Na + O2 → 2Na2O
Trends in Physical Properties of Alkali Metals
- Alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).
- Physical properties vary with increasing atomic number: melting and boiling points decrease.
- Alkali metals are soft, with a characteristic silvery luster, becoming more malleable as you move down the group.
- Density generally increases down the group, with lithium being less dense than water.
- Higher reactivity accompanies lower ionization energies, which decrease as you move down the group.
Chemical Properties of Alkali Metals
- Alkali metals react vigorously with water to produce hydroxides and hydrogen gas, releasing heat.
- Reactivity increases down the group; lithium reacts moderately, while cesium is explosively reactive.
- Alkali metals form ionic compounds with halogens; the halide salts are typically soluble in water.
- Reactions with oxygen form oxides (Li2O), peroxides (Na2O2), or superoxides (KO2), depending on the metal.
Trends in Reactivity of Alkali Metals
- Reactivity increases down the group due to lower ionization energies, making it easier to lose the outermost electron.
- Cesium is the most reactive, while lithium is the least reactive.
- Alkali metals must be stored under oil or inert gas to prevent reactions with moisture and air.
Writing Balanced Equations for Reactions of Alkali Metals
- Example reaction with water:
- 2Na + 2H2O → 2NaOH + H2↑
- Example reaction with halogens:
- 2K + Cl2 → 2KCl
- Example reaction with oxygen (for sodium):
- 4Na + O2 → 2Na2O
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Description
Explore the physical and chemical characteristics of alkali metals including lithium, sodium, and potassium. This quiz covers trends in reactivity, density, and ionization energies as you move down the group. Test your knowledge on how these elements interact with water and halogens.
