Elements are organized on the periodic table based on their properties. Which statement correctly predicts and explains the chemical reactivity of two metals?
a. Rubidium (Rb) is more reactive than strontium (Sr) because strontium atoms must lose more electrons.
b. Sodium (Na) is more reactive than magnesium (Mg) because sodium atoms must gain more electrons.
c. Calcium (Ca) is less reactive than potassium (K) because potassium atoms must lose more electrons.
d. Beryllium (Be) is less reactive than lithium (Li) because beryllium atoms must gain more electrons.

The ionization energy (Ei) is the minimum amount of energy required to remove the valence electron, when element lose electrons, oxidation number of element grows (oxidation process).

Alkaline metals (group 1), in this example rubidium, have lowest ionizations energy and easy remove valence electrons (one electron), they are most reactive metals.

Earth alkaline metals (group 2), in this example strontium, have higher ionization energy than alkaline metals, because they have two valence electrons, they are less reactive.

Rubidium electron configuration: ₃₇Rb 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s¹; one valence electron is 5s¹ orbital.

Strontium electron configuration: ₃₈Sr 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s²; two valence electrons is 5s² orbital.

snehapa snehapa · Answer 2 · 2019-09-23T11:36:13+02:00

The correct statement about the reactivity of metal is option A, rubidium (Rb) is more reactive than strontium (Sr) because strontium atoms must lose more electrons.

Further explanation:

Reactivity is defined as the tendency of the element to lose or gain an electron.

The reactivity trend of metals in periodic table:

Across a period, the energy level remains same while the number of electrons increases. This causes an increase in nuclear charge of the atom. Therefore electrons are strongly held by the nuclear forces. As a result, the reactivity of metals decreases from left to right.

Down the groups, the energy level increases while the number of electrons remains same. This causes a decrease in nuclear charge of the atom. Therefore electrons are loosely held by the nuclear forces. As a result the reactivity of metals increases from top to bottom.

A. Rubidium (Rb) is more reactive than strontium (Sr) because on moving left to right in period reactivity of metal decreases. Also, in strontium electrons are more tightly held with nucleus, and it must lose more electron. This option is correct.

B. Sodium (Na) is more reactive than magnesium (Mg) because on moving left to right in period reactivity of metal decreases. Also, the magnesium atom has to lose more electron. So, the given reason for option B is wrong.

C. Calcium (Ca) is less reactive than potassium (K) because on moving left to right in period reactivity of metal decreases. Also, the calcium atom has to lose more electron. So, the given reason for option C is wrong.

D. Beryllium (Be) is less reactive than lithium (Li) because on moving left to right in period reactivity of metal decreases. Also, the beryllium atom has to lose more electron. So, the given reason for option D is wrong.

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Answer details:

Grade: Senior school

Subject: Chemistry

Chapter: Periodic table

Keywords: Periodic table, reactivity, metal reactivity, rubidium, strontium, sodium, magnesium, calcium, potassium, beryllium, lithium, more reactive metal.