1) Atomic number of argon (Ar) is 18, it way that it has actually 18 protons and 18 electrons.

You are watching: Write the chemical symbols for three different atoms or atomic anions with 18 electrons.

Electron construction of argon atom: ₁₈Ar 1s² 2s² 2p⁶ 3s² 3p⁶.

2) Atomic number of chlorine (Cl) is 17, it method that it has actually 17 electrons and also 17 protons, yet if it obtain one electron, it becomes anion Cl⁻ v 18 electrons.

Electron construction of chlorine anion: ₁₇Cl⁻ 1s² 2s² 2p⁶ 3s² 3p⁶.

3) Atomic variety of sulfur (S) is 16, it means that it has actually 16 electrons and 16 protons, but if it get two electrons, it i do not care anion S²⁻ with 18 electrons.

Electron configuration of sulfur anion: ₁₆S²⁻ 1s² 2s² 2p⁶ 3s² 3p⁶.

Three various atoms or atom anions with 18 electrons: Cl⁻, K⁺, Ar

Further explanation

The atom Number (Z) indicates the number of protons in one atom of an element. If the atom is neutral climate the variety of protons will certainly be equal to the number of electrons. Therefore the atom number can additionally indicate the number of electrons.

So atom number = number of protons = number of electrons

Mass Number (A) is the sum of protons and neutrons

Mass Number (A) = number of protons + number of Neutrons

So that the relationship in between atomic numbers and also mass numbers have the right to be formulated as follows:

Atomic Number (Z) = massive Number (A) - number of Neutrons

In the following aspect notation,

Information

X = symbol of elemental atom

A = mass number

= variety of protons + variety of neutrons

Z = atomic number

= number of protons = number of electrons, on neutral elements

In one atom, there are levels of energy in the skin and sub skin.

This energy level is to express in the kind of electron configurations.

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Charging electron in the sub skin uses the adhering to sequence:

1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p⁶, 6s², etc.

The place of the aspect group in the periodic device is identified by the variety of valence electrons that fills the critical sub-skin

The element period is identified from the valence shell (the largest main quantum number (n))

Atoms or ionic atom that have 18 electrons include:

1. Atom: Ar: 1s² 2s² 2p⁶ 3s² 3p⁶2. Atom ion

a. Cl: 1s² 2s² 2p⁶ 3s² 3p⁵

because it records 1 much more electron to it is in stable choose the noble gas Ar so that the electron configuration has 18 electrons