Question

q1 chemistry: u2l5
prework part 1: periodic table practice

1. **label the periodic table below using the groups discussed in class. indicate which group(s) represent(s) the alkali metals, alkaline earth metals, transition metals, halogens, and noble gases.
2. shade the nonmetals in dark pencil, metalloids with light pencil, and leave the metals unshaded.
3. use your notes from class to answer the following questions:

a. **what is a period? a row
b. **what is a group? a column
c. **how many valence electrons does sodium have?
d. *how many valence electrons does nitrogen have?
e. *how many valence electrons does xenon have?
f. **why are noble gases the most stable?
g. which group of elements is the most reactive with water?

Explanation:

Step1: Recall electron - configuration rules

Valence electrons are the electrons in the outermost shell. Sodium (Na) has an atomic number of 11. Its electron - configuration is 1s²2s²2p⁶3s¹. So it has 1 valence electron.

Step2: Recall nitrogen's electron - configuration

Nitrogen (N) has an atomic number of 7. Its electron - configuration is 1s²2s²2p³. So it has 5 valence electrons.

Step3: Recall xenon's electron - configuration

Xenon (Xe) has an atomic number of 54. Its electron - configuration ends with 5s²5p⁶. So it has 8 valence electrons.

Step4: Explain noble gas stability

Noble gases have a full outer shell of electrons (either 2 for helium or 8 for the others), which gives them a stable electron configuration and makes them unreactive.

Step5: Identify most reactive group with water

Alkali metals (Group 1) are the most reactive with water because they have one valence electron and readily lose it to form a positive ion.

Answer:

c. 1
d. 5
e. 8
f. They have a full outer - shell of electrons, giving them a stable electron configuration.
g. Alkali metals (Group 1)