Question

beryllium - 9
step 1. the atomic number of beryllium - 9 is _.
step 2. its mass number is _.
step 3. the shorthand notation for beryllium - 9 is:

step 4. is your answer reasonable? why?

4.3 distinguishing among atoms

1. the identity of an element is determined by the number of _ it contains.
2. each of an elements _ has a different number of neutrons and a different mass number.
3. the _ of an element is the weighted average of all the isotopes of the element.

Explanation:

Step 1: Determine atomic number

The atomic number of beryllium (Be) is \(4\) (from the periodic table).

Step 2: Determine mass number

The mass number is given as \(9\) (from the name beryllium - 9).

Step 3: Write shorthand notation

The shorthand notation for an element is \(\ce{^{A}_{Z}X}\), where \(A\) is the mass number and \(Z\) is the atomic number. So for beryllium - 9, it is \(\ce{^{9}_{4}Be}\).

Step 4: Check reasonability

The atomic number \(4\) is correct as beryllium is the 4th element in the periodic table. The mass number \(9\) is consistent with the name beryllium - 9. The shorthand notation follows the standard \(\ce{^{A}_{Z}X}\) format.

For questions 7 - 9:

Question 7

The identity of an element is determined by the number of protons it contains.

Question 8

Each of an element's isotopes has a different number of neutrons and a different mass number.

Question 9

The atomic mass of an element is the weighted average of all the isotopes of the element.

Answer:

Step 1: \(4\)
Step 2: \(9\)
Step 3: Top box: \(9\), bottom box: \(4\)
Step 4: Yes, because atomic number \(4\) (from periodic table), mass number \(9\) (from name), notation follows \(\ce{^{A}_{Z}X}\) format.

1. protons
2. isotopes
3. atomic mass