Question

part 3: continued...

1. how does the number of electrons change as you move from left to right across a period?
2. what do all the atoms of group 1a elements have in common?
3. list three things that all the atoms of the elements in period 3 have in common.
4. which atoms have two electrons in the first shell, and eight electrons in the second shell?

what happens to the electron count and the number of shells when you move from neon (ne) to sodium (na)?
draw a shell model of an atom with two shells, and six electrons.

Explanation:

Step1: Analyze electron - change across a period

As you move from left to right across a period, the atomic number increases by 1 for each successive element. Since the number of electrons in a neutral atom is equal to its atomic number, the number of electrons increases by 1.

Step2: Identify common feature of Group 1A elements

All atoms of Group 1A elements have 1 valence electron in their out - most shell.

Step3: List common features of period 3 elements

All atoms of elements in period 3 have 3 electron shells. They also follow the trend of increasing atomic number and number of electrons from left to right. And they are in the same principal energy level (n = 3).

Step4: Find atoms with specific electron configuration

Atoms with two electrons in the first shell and eight electrons in the second shell are noble gases in the second period. Neon (Ne) is such an atom.

Step5: Analyze change from Ne to Na

Neon (Ne) has 10 electrons and 2 electron shells. Sodium (Na) has 11 electrons and 3 electron shells. So when moving from Ne to Na, the electron count increases by 1 and the number of shells increases by 1.

Answer:

1. The number of electrons increases by 1 as you move from left to right across a period.
2. All atoms of Group 1A elements have 1 valence electron.
3. Three things that all atoms of elements in period 3 have in common are: they have 3 electron shells, they follow the trend of increasing atomic number and number of electrons from left - to - right, and they are in the same principal energy level (n = 3).
4. Neon (Ne) has two electrons in the first shell and eight electrons in the second shell.
5. When moving from neon (Ne) to sodium (Na), the electron count increases by 1 and the number of shells increases by 1.