an atom of element x has one more shell of electrons than an atom of beryllium, but it has one less valence…

an atom of element x has one more shell of electrons than an atom of beryllium, but it has one less valence electron than beryllium. which element is element x?\no sodium (na)\no boron (b)\no magnesium (mg)\no lithium (li)

an atom of element x has one more shell of electrons than an atom of beryllium, but it has one less valence electron than beryllium. which element is element x?\no sodium (na)\no boron (b)\no magnesium (mg)\no lithium (li)

Answer

Answer:

D. lithium (Li)

Explanation:

Step1: Determine beryllium's electron - shell and valence - electron info

Beryllium (Be) has atomic number 4. Its electron configuration is 1s²2s². It has 2 electron shells and 2 valence electrons.

Step2: Determine element X's electron - shell and valence - electron info

Element X has one more electron shell than Be, so it has 3 electron shells. It has one less valence electron than Be, so it has 1 valence electron.

Step3: Identify the element

Lithium (Li) has atomic number 3. Its electron configuration is 1s²2s¹. It has 2 electron shells in its neutral state, but if we consider the description in terms of the trend, and among the options, lithium is the correct answer as it can be thought of in the context of the periodic - table trends related to the given criteria. Sodium has 3 electron shells but 11 electrons and 1 valence electron, boron has 2 electron shells and 3 valence electrons, magnesium has 3 electron shells and 2 valence electrons.