Answer :
Answer:
Potassium (K)
Explanation:
When a group 1 metal forms a positive ion, it loses one electron. This means they form 1+ ions. Argon will not form ions as it has a fuller outer shell of electrons, so it is electronically stable. An atom of Argon has 18 electrons, so you need to find the group 1 metal where, when you subtract one from it's atomic number (which is the number of protons in one atom) it equals 18. The proton number for an atom is the same as the electron number in an atom, atoms are neutrally charged so their positively charged protons equal their negatively charged electrons. When they become charged, that's what an ion is. Potassium (K) has 19 electrons, when you take one away from that, it forms a K+ ion, with 18 electrons, equalling that to Argon. I hope this makes sense!
Group 0 elements are found at the right-most column of the Periodic Table.
Argon has the abbreviation "Ar" and it is atomic number 18. Meaning it has 18 protons and 18 electrons. The proton and electron counts are equal to balance out the overall net charge.
Our mystery element in group 1 is somewhere in the left-most column of the Periodic Table. Any element in this column has exactly one electron in its outer-most shell. When forming a positive ion, this lone electron will be lost to another element. Notice that losing a negative charge will result in an overall charge of +1, i.e. there's one more positive charge (proton) compared to negative charge (electron).
Example: Sodium chloride (NaCl), aka rock salt, is the combination of sodium (element abbreviation "Na") and chlorine (abbreviation "Cl"). The sodium will lose the outer-most electron to the chlorine, so that both elements will have full outer shells after both elements react to each other.
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Anyways, we're looking for some element in group 1 such that taking one electron away will result in 18 electrons. So we're looking for something that has 18+1 = 19 electrons to start off with. This will lead to 19 protons and element 19 potassium. The symbol for potassium is the letter "K". The K refers to the Latin word Kalium.
