Question

mass number = big number
atomic number = smaller number
protons = small #
electrons = small #
neutrons= big # - small #
1st shell can hold a maximum of 2 electrons
2nd shell can hold a maximum of 8 electrons
3rd shell can hold 8 electrons
4th shell can hold 8 electrons
chlorine, cl

1. atomic # = 17
2. mass # = 35.5
3. protons =
4. neutrons =
5. electron =
6. e.c=
7. what is the valence (the last number in the e.c) electron?
8. what group is cl in the periodic table? group (hint: the last # in the ec tells the group #)
9. what period is cl in the periodic table? period (hint the amount of # in the ec tells the period #)

Explanation:

Step1: Find number of protons

Protons = Atomic number = 17

Step2: Calculate number of neutrons

Neutrons = Mass number - Atomic number = $35.5 - 17 = 18.5$

Step3: Find number of electrons

Electrons = Atomic number = 17

Step4: Determine electron configuration

Fill shells to max capacity: 1st shell (2), 2nd shell (8), remaining $17-2-8=7$ in 3rd shell. So E.C = 2,8,7

Step5: Identify valence electrons

Valence electrons = last number in E.C = 7

Step6: Find periodic table group

Group number = valence electrons = 17 (or 7A)

Step7: Find periodic table period

Period number = number of shells in E.C = 3

Answer:

1. Protons = 17
2. Neutrons = 18.5
3. Electron = 17
4. E.C= 2,8,7
5. Valence electron = 7
6. What group is Cl in the periodic table? Group 17 (or 7A)
7. What PERIOD is Cl in the periodic table? Period 3