A certain atom consists of 16 protons, 18 neutrons, and 16 electrons. What is its atomic number, mass number, and electron configuration?

1 Answer
Dec 21, 2015

Answer:

Here's what I got.

Explanation:

So, you know that your atom contains

  • #16# protons
  • #18# neutrons
  • #16# electrons

Right from the start, you know that you're indeed dealing with a neutral atom, since the number of protons it has in its nucleus is equal to the number of electrons it has surrounding its nucleus.

Now, an atom's atomic number, #Z#, tells you how many protons it has in its nucleus. Nothing more, nothing less.

In your case, you are told that the atom contains #16# protons in its nucleus, which means that #Z# will be equal to

#Z = 16#

A quick look in the periodic table will reveal that you're dealing with an atom of sulfur, #"S"#.

An atom's mass number, #A#, tells you how many protons and neutrons it contains in its nucleus. Since the number of protons is given by #Z#, you can say that

#A = Z + "no. of neutrons"#

In your case, the atom contains #18# neutrons in its nucleus. This means that #A# will be equal to

#A = 16 + 18 = 34#

Finally, focus on the atom's electron configuration, which you know that must account for a total of #16# electrons.

#"S: " 1s^2 2s^2 2p^6 3s^2 3p^4#

Its noble gas shorthand notation, which uses the electron configuration of neon, #"Ne"#, the noble gas that comes before sulfur in the periodic table, will look like this

#"S: " ["Ne"] 3s^2 3p^4#