Science

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How two neutral objects may become positively and negatively charges?
How is atomic mass established?
Which atoms will form covalent bonds and which atoms will form ionic bonds?

  • Science -

    Losing one or more electrons will make a neutral object positive. Gaining one or more electrons will make a neutral object negative.

    The atomic mass of an element, consisting primarily of the protons and neutrons, is established by comparing the mass of that element with 6 12C set at exactly 12.00000.

    Compounds formed between elements on the left hand side of the periodic table and the right hand side of the periodic table generally are ionic. Compounds formed between similar (or the same) elements generally are covalent.

  • Science -

    for the established part...i don't get what is "6^12C set at exactly 12.00000"

  • Science -

    can you simplify the meaning for the third part too...thanx...because i think i am confusing myself...so the covalent is usually the left side and the ionic are usually on the right side...right?

  • Science -

    Atomic masses are established by comparing the mass of an element to that of carbon (not just any carbon atom but the carbon atoms (carbon isotope, that is) with 6 protons, 6 neutrons, and 6 electrons) and calling that mass exactly 12.0000. In the very early days of chemistry the actual mass of an atom was not known and there was no way to get it; however, comparisons were easy to do. Therefore, the early chemists compared the mass of an element to another element and set the stomic mass of the "standard" element to some artificial number. That standard element has evolved through the years but it is now carbon-12.(When I was in school it was oxygen-16 but that was changed in the '60s.)

    No about the third part. Compounds between elements on different sides of the tbe table generally are ionic. For example, K with F, Cl, Br, etc or O, S, etc to form KF, KCl, K2O, K2S etc (look where those are on the periodic table) are ionic. Ba or Sr with O, S, F, Cl etc to form BaO, BaS, BaCl2, BaF2, etc are ionic (look for the position of those elements.) That is what I mean by elements on the left side combining with element on the right side. But elements that are the similar (or if they are the same) generally form covalent bonds. For example, Cl + Cl is Cl2 and that is a covalent bond between two atoms of the same element. Br2, Cl2, F2, H2, all are atoms forming a covalent bond with itself. C and H forms many compounds but these are compounds between elements NOT on different sides of the table (Look at C and you will see it is in the middle and it is combing with an element on the left side of the table.)
    Or Br and Cl are elements on the same side of the table. BrCl is a covalent bond. OF2 is a covalent bond. SO2 and SO3 are covalent bonds between O and S. I hope this helps.

  • Science -

    so...what you mean is that ionic bonds attract (mostly) opposite properties elements and covalent bonds attract similar elements

  • Science -

    I think what you have said is inherently wrong; however, I know what you are trying to say and you have the right idea. You just haven't stated it correctly. So let's work on getting it right. The two main problems I have with your statement is that (a)ALL elements have different properties and (b) ionic bonds and covalent bonds don't attract elements.

    Looking at K and F, K is a metal and F is a non-metal. Compounds between highly metallic elements (K, Na, Ba, Sr, Cs====elements in groups IA and IIA) and highly non-metallic elements (F, Cl, O, S====elements in groups VIA and VIIA) generally are ionic. So the metal versus non-metal character is one point you can use. [By the way, I don't know what system your teacher is using for numbering the columns of the periodic table==your prof may have IA and IIA numbered as 1 and 2 and columns VIA and VIIA numbered as 16 and 17.] What is left are compounds between metal and metal (covalent), non-metal and non-metal (covalent).

    Have you studied electronegativity? Another way you can look at it is comparing electronegativity (EN) values. The metals (those on the left side of the table) are highly electropositive and the non-metals (those on the right of the table) are electronegative. Ionic bonds are formed when an electropositive atom combines with an electronegative atom. You can even put numbers to this. For example, the EN of F is 4.0 and that of Cs is 0.8. The difference is 3.2. A compound between elements with a difference 1.9 in EN value is ionic. If we combine H with H we have (of course) 2.1-2.1 = 0 and that is covalent. C and H is 2.4 - 2.1 = 0.3 and that is covalent. OF2 is 4.0-3.5 = 0.5 and the bond is covalent.
    I hope this clears up any confusion. Again, I think you had the right idea but this will restate what you said.

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