The least active metal of those represented below has an electron configuration abbreviated

Mg is the least active metal

The periodic system of elements is an arrangement of elements classified based on similar properties and their atomic number order.  

The periodic system is divided into groups (vertical order) and periods (horizontal order)  

In one group, from top to bottom, the first ionization of energy tends to get smaller, because the addition of electron shells makes the attraction of the atomic nucleus to the outer electrons (valence electron) weaker, so that it is easily released, forming cations +  

We complete the available answer choices

1. [Ne]3s²

2. [Ar]4s²

3. [Kr]5s²

4. [Xe]6s²

If we see from the electron configuration, the elements above are included in group 2A (have 2 valence electrons)

the atomic number of elements in group 2A from electron configuration above :

• Mg : 12,  [Ne]3s²

• Ca : 20,  [Ar]4s²

• Sr : 38,  [Kr]5s²

• Ba: 56,  [Xe]6s²

Shows that, the element is getting down, the shell electron is increasing, so that in one group, from top to bottom, the radius of the atom tends to get bigger, according to the electron shell increase.  

From top to bottom, the easier the elements release electrons, and the more reactive  

This reactivity causes a very large reaction to water and water  

So that from group 2A, Mg is the least active metal

electron affinity  

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Identify the group number in the periodic table  

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the charge on each ion in the compounds  

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it means there are 3 atoms of oxygen

fe 55.85 g/mol and h2o 18.02 g/mol.