Question

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Below are the Bohr models of three different neutral atoms. The solid black circle in the middle represents the nucleus. The concentric circles represent the shells or principle energy levels. The red dots represent the electrons present in each shell or principle energy level.

#14 Identify the three elements represented in the Bohr models above and then describe the position of each element on the periodic table.

#15 Place the three elements in order of DECREASING atomic radius and explain why.

Answer 1

Answer:

14. Be, Mg, Ca in Group 2.

15. Ca > Mg > Be

Step-by-step explanation:

14. Identify the elements.

Atom A has the shell configuration 2, 2.

It has four electrons, so it is Element 4 in the Periodic Table: Be (beryllium).

Atom B has the shell configuration 2, 8, 2.

It has 12 electrons, so it is Element 12 in the Periodic Table: Mg (magnesium).

Atom C has the shell configuration 2, 8, 8, 2.

It has 20 electrons, so it is Element 20 in the Periodic Table: Ca (calcium).

Each element has two electrons in its outermost shell, so they all belong in Group 2 of the Periodic Table.

15. Order of atomic radii

The Figure below shows the position of the elements in Group 2.

As you go down the Group, the atoms get bigger, because each atom has one more electron shell than the one above is, and each shell is bigger than the one before it.

Thus, the atomic radius increases in the order Be < Mg < Ca.  

However, "they" want the order of decreasing radius, so we must go up the Group.

The elements in order of decreasing radius are

Ca > Mg > Be.

Answer 2

14. 1st has 4 e- so it is Be, 2nd has 12 e- so it is Mg, 3rd has 20 e- so it is Ca. they are all in Group II in the periodic table with Be in 2nd row, Mg in the 3rd row n Ca in the 4th row.

15. as each element has more electrons, filling up more electron shell, the atomic radius gets bigger n bigger. In decreasing order, Ca, Mg and Be.