Group 1 Flashcards

All 12 cards in this deck

Why is sodium classified as an alkali metal?

It is in group 1, the first column on the left of the periodic table, so its atoms have 1 electron in the outer shell (Na is 2.8.1).

Recall two physical properties of the alkali metals.

They are soft and have relatively low melting points.

True or false? Like most other metals, alkali metals are hard and have high melting points.

False. Alkali metals are soft and have relatively low melting points (e.g. potassium melts at about 63 °C).

What would you see when a small piece of sodium is dropped onto water?

Effervescence (bubbles/fizzing), the metal melts into a ball and moves quickly on the surface, and it gets smaller and disappears.

What are the steps to write the balanced symbol equation, with state symbols, for an alkali metal reacting with water?

e.g. potassium and water

1. Products are the metal hydroxide + hydrogen: KOH and $\mathrm{H_2}$
2. Balance: $2\mathrm{K} + 2\mathrm{H_2O} \rightarrow 2\mathrm{KOH} + \mathrm{H_2}$
3. Add state symbols: $2\mathrm{K}(s) + 2\mathrm{H_2O}(l) \rightarrow 2\mathrm{KOH}(aq) + \mathrm{H_2}(g)$

What effect does the solution left after an alkali metal reacts with water have on universal indicator?

It turns universal indicator blue/purple — the metal hydroxide solution is alkaline (pH above 7).

What is the trend in reactivity with water going down group 1 from lithium to sodium to potassium?

Reactivity increases down the group: lithium is least reactive, then sodium, then potassium.

When equal-sized pieces of lithium, sodium and potassium are added to water, why is a flame produced only with potassium?

Potassium is the most reactive of the three, so its reaction with water releases enough energy to ignite the hydrogen.

What would you see when a small piece of rubidium is dropped onto water?

Effervescence, the metal disappears, and it ignites/explodes — an even more violent reaction than potassium's.

In terms of electronic configurations, why does reactivity increase down group 1?

e.g. potassium (2.8.8.1) is more reactive than lithium (2.1)

Atoms have more shells, so the outer electron is further from the nucleus and more shielded; attraction is weaker, so the outer electron is lost more easily by potassium than by lithium.

True or false? Alkali metals get more reactive down the group because their atoms have more electrons in the outer shell.

False. Every group 1 atom has 1 outer electron; the outer electron is further from the nucleus and more shielded down the group, so it is lost more easily.

What charge do ions of group 1 elements have, and what is the equation for the ion forming?

e.g. sodium, 2.8.1

$+1$; $\mathrm{Na} \rightarrow \mathrm{Na^+} + \mathrm{e^-}$, so the ion is 2.8.