Question

the diagram shows the electron configuration of an atom of an element for the electrons in the s and p orbitals. what is the group number of the element in the periodic table? options: 1, 2, 13, 15

Explanation:

Step1: Determine valence electrons

The electron - dot diagram (Bohr model) shows the electron distribution in shells. The outermost shell electrons (valence electrons) determine the group number (for main - group elements). Let's count the electrons in the outermost shell. From the diagram, the outermost shell (the largest circle) has 3 electrons? Wait, no, let's re - examine. Wait, the electron configuration: the innermost shell (first shell) can hold 2 electrons, the second shell can hold up to 8, and the outermost (valence) electrons. Wait, looking at the diagram, the outermost shell (the third shell? Wait, no, the circles: the innermost circle (nucleus - like) then two inner shells? Wait, no, the standard Bohr model: the first shell (closest to nucleus) has 2 electrons (the two small dots), the second shell has 8? No, wait the diagram: the innermost (first) shell: 2 electrons (the two black dots close to the nucleus), the second shell: let's see, no, the outermost shell (the largest circle) has 3 electrons? Wait, no, the group number for main - group elements is equal to the number of valence electrons (for groups 1 - 2 and 13 - 18). Wait, let's count the valence electrons. The outermost shell electrons: in the diagram, the outermost shell (the third shell? Wait, the circles: the first shell (nucleus - adjacent) has 2 electrons, the second shell has 8? No, the diagram shows: the innermost (first) shell: 2 electrons, the second shell: 8? No, the middle shell (second) has 8? Wait, no, the diagram: the nucleus (dark circle), then a shell with 2 electrons (the two small black dots), then a shell with 8? No, the outermost shell (the largest circle) has 3 electrons? Wait, no, the options are 1, 2, 13, 15. Wait, group number: for main - group elements, group number = number of valence electrons (for groups 1 - 2) or 10 + number of valence electrons (for groups 13 - 18). Wait, if the valence electrons are 3, then group number is 13 (since 10+3 = 13). Let's check the electron count. The total number of electrons: first shell (2) + second shell (8) + third shell (3)? Wait, no, maybe the electron count is: let's see, the first shell (n = 1) has 2, second shell (n = 2) has 8, third shell (n = 3) has 3. So the element has atomic number 2 + 8+3 = 13. The group number for an element with atomic number 13 (aluminum) is 13 (since it's in group 13 of the periodic table, and the number of valence electrons is 3, and for group 13, group number = 13).

Step2: Match with group number

The group number of an element with 3 valence electrons (main - group element) is 13 (because group 13 elements have 3 valence electrons). Among the options, 13 is an option.

Answer:

13