Some atoms have nearly eight electrons in their valence shell and can gain additional valence electrons until they have an octet. When these atoms gain electrons, they acquire a negative charge because they now possess more electrons than protons. Negatively charged ions are called anions. Most nonmetals become anions when they make ionic compounds.
We can use electron configurations to illustrate the electron transfer process between sodium atoms and chlorine atoms. As demonstrated here, a sodium atom Na has one valence electron in the third principal energy level. It is likely to achieve an octet in its outermost shell by losing its one valence electron. It is now the same as that of the noble gas neon.
The term isoelectronic refers to an atom and an ion of a different atom or two different ions that have the same electron configuration. The sodium ion is isoelectronic with the neon atom. The equation below illustrates this process. When a chlorine atom gains an electron, its outermost principal energy level achieves an octet.
In this case, the ion has the same outermost shell as the original atom, but now that shell has eight electrons in it. Once again, the octet rule has been satisfied. This process is illustrated below. In table salt, this electron comes from the sodium atom. With two oppositely charged ions, there is an electrostatic attraction between them because opposite charges attract. The resulting combination is the compound sodium chloride.
Notice that there are no leftover electrons. The number of electrons lost by the sodium atom one equals the number of electrons gained by the chlorine atom one , so the compound is electrically neutral. In macroscopic samples of sodium chloride, there are billions and billions of sodium and chloride ions, although there is always the same number of cations and anions. Write the formula of the resulting ion and its electron configuration. The electron configuration of Al atom is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 1.
The second shell has octet 2 s 2 2 p 6 while the valence shell has 3 electrons 3 s 2 3 p 1. Mg can achieve octet by losing the 3 valence electrons.
The electron configuration of O atom is 1 s 2 2 s 2 2 p 4. The second shell has six electrons 2 s 2 2 p 4 and needs two electrons to achieve octet. Oxygen will gain 2 electrons. In many cases, elements that belong to the same group vertical column on the periodic table form ions with the same charge because they have the same number of valence electrons.
Thus, the periodic table becomes a tool for remembering the charges on many ions. The name "chlorine" refers to a neutral Cl atom, so how do we denote the anion? Anions are often, but not always, indicated with the suffix -ide. A Cl ion with a charge of —1 has the name "chloride. To work in reverse, consider the compound ammonium sulfate.
To combine these species into a neutral ionic compound, we need two ammonium ions for every sulfate ion. The proper formula here, then, is NH 4 2 SO 4. The parentheses around SO 4 are optional, but I like to use them to show that the sulfur and oxygen atoms are bound covalently to one another but not to the atoms of the ammonium cation. Below, you'll find lists of commonly encountered cations and anions. You can also practice your naming skills using this page and this page.
Barite forms in proportion to ocean productivity - the activity of marine phytoplankton the floating "trees" of the ocean which are the base of the marine food chain - and accumulates in marine sediments. The accumulation of barite in ocean sediments can tell us how productive the ocean was at any given time in Earth's history.
Barite in contrast to many other minerals is not soluble and is preserved over many millions of years recording the chemistry of the ocean and how it changed over time.
Chemist Adina Payton telling the tale of barium. And talking of what sits at the bottom of the oceans. The smell of the sediment tells a great deal about the underlying chemistry. Thick black anoxic sediments can be accompanied by a putrid smell which is unique to reduced sulfur. Maybe this is why sulfur has such a bad reputation. My son wouldn't eat eggs for 6 months when he got a smell of his first rotten one. That's the stinky story of sulfur with Steve Mylon on next week's Chemistry in its element, I hope you can join us.
I'm Chris Smith, thank you for listening and goodbye. Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists. There's more information and other episodes of Chemistry in its element on our website at chemistryworld.
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Political stability of top reserve holder. Young's modulus GPa. Shear modulus GPa. Bulk modulus GPa. Vapour pressure. Temperature K. Pressure Pa. Listen to Barium Podcast. Transcript : Chemistry in its element: barium Promo You're listening to Chemistry in its element brought to you by Chemistry World , the magazine of the Royal Society of Chemistry.
End promo Chris Smith Hello, this week rat poison, fireworks, fine glass, oil exploration and enemas. Adina Payton For many, barium has an unpleasant association. And therefore it's a great archive of ocean history.
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