Question

1. if an atom has 17 protons, 18 neutrons, and 17 electrons, its mass number is: a) 17 b) 34 c) 35 d) 18 7. a neutral atom of calcium (atomic number 20) has how many electrons? a) 10 b) 20 c) 40 d) 60

Explanation:

Step1: Recall the formula for mass number

The mass number \(A\) of an atom is given by the sum of the number of protons \(p\) and neutrons \(n\), i.e., \(A=p + n\).

Step2: Substitute the values

Given \(p = 17\) and \(n=18\), then \(A=17 + 18\).

$$A=35$$

Step3: Recall the property of a neutral atom

For a neutral atom, the number of electrons \(e\) is equal to the number of protons \(p\) (which is equal to the atomic number \(Z\)).

Step4: Apply the property to calcium

Given the atomic number of calcium \(Z = 20\). For a neutral calcium atom, \(e=Z\), so \(e = 20\).

Answer:

1. C. 35
2. B. 20