## 2 simple questions about periodic table...

hello can some one help me to answer these 2 questions...
1.how many unpair electrons are there in the Cr+3 ion?
a)0
b)1
C)3
d)6

2.Two particles have the followinf composition:
A 37 protons; 38 neutrons; 37 electrons
B 37 protons; 40 neutrons; 37 electrons

a) what is the relationship between these particles?
b) these two particles have very similar chemical properties. Explain why.[/sup]

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### How do you find the number

How do you find the number of neutrons if you know the number of electrons?

### You don't! The number of

You don't! The number of neutrons can vary according to the isotope of the element. You can find the possible numbers of neutrons, by identifying the element by number. The number of electrons will equal the atomic number, unless a charge (e.g. +2, -1...) is specified. Then by looking at the list of isotopes, and subtracting the atomic number (the number of protons) you can say how many neutrons could be in the nucleus. -RD

### Re: 2 simple questions about periodic table...

[quote="valen_restrepo"]hello can some one help me to answer these 2 questions...
1.how many unpair electrons are there in the Cr+3 ion?
a)0
b)1
C)3
d)6

2.Two particles have the followinf composition:
A 37 protons; 38 neutrons; 37 electrons
B 37 protons; 40 neutrons; 37 electrons

a) what is the relationship between these particles?
b) these two particles have very similar chemical properties. Explain why.[/sup][/quote]
1. Cr(3+) has 3 unpaired electrons; it starts off with 6 valence electrons, and you have removed 3; 6-3=3.
2. A and B both have 37 protons (and 37 electrons)
The 37th element of the periodic table?
I'd say look it up, but I'm in a generous mood (Rb)
The only difference between A and B is the number of Neutrons; A and B are different isotopes of Rubidium (75Rb and 77Rb; the number in superscript)

WebElements: the periodic table on the WWW [http://www.webelements.com/]