"Would you expect each of the following atoms to gain or lose electrons when forming ions? What ion [cation/anion] is most likely in each case?"
Followed by a short list of elements such as Na and Sr. What I'm wondering is how I'm to know? I can't find anything in the text explaining when an atom will lose electrons rather than gaining them, only that they /do/.
3 answers
Sure, just think about the periodic table and how it works. Elements in group I (Li,Na, K, Rb, etc) have 1 electron in their outside shell. Thus, by losing 1 electron they become an + ion and the inner shells are full. Same for group II elements (Mg, Ca, Sr, Ba, etc) except they have 2 electrons in their outside shell sos they lose 2. Now take a look at group 17 (F, Cl, Br, I etc). They have 7 electrons in their outside shell; therefore, the want to gain an electron to make that outside shell full with 8 and it gives them a minus 1 charge. Same, more or less for group 16 elements (O, S, etc), Thus you get the trend. Those elements on the left part of the table want to lose electrons and those on the right side of the table want to gain electrons. The most electropositive elements want to lose electrons and the most electronegative elemnets want to gain electrons. I don't know if you have studied electronegativity but that is the way to know if they gain, lose, or share electrons. The GENERAL rule is that elements in group 1 and 2 form + 1 and +2 ions, respectively, when combining with elements in group 16 and 17, with those latter elemnets becoming -1 and -2 charged respectively.
I see, thanks.
Is it safe to say that when the periodic table is divided evenly in two, the elements on the left will always lose electrons when forming ions, and vice versa?
Is it safe to say that when the periodic table is divided evenly in two, the elements on the left will always lose electrons when forming ions, and vice versa?
No it isn't safe to say that. It is safe to say that many metals lose electrons and many non-metals gain electrons but the table isn't divided evenly between metals and non-metals. Furthermose, those elmeent in the middle (as the transition is made from metals to non-metals) are called metalloids (or perhaps amphoteric elements) and they can act as both metals and non-metals, depending upon what they react with. Finally, if you draw a diagonal (lay a ruler or straight edge) beginning at element 5 and moving diagonally down and to the right to Si, As, Te, At (you see a broken line there that looks a little like this:
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etc). That line more less divides the metals on the left from the non-metals on the right with the elements on the edges of the straight edge as metalloids.
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etc). That line more less divides the metals on the left from the non-metals on the right with the elements on the edges of the straight edge as metalloids.
1 answer