Why does pb have a 2 charge

It is conventional to use the lowest ratio of ions that are needed to balance the charges. Each ion has a single charge, one positive and one negative, so we need only one ion of each to balance the overall charge. When writing the ionic formula, we follow two additional conventions: 1 write the formula for the cation first and the formula for the anion next, but 2 do not write the charges on the ions.

The formula Na 2 Cl 2 also has balanced charges, but the convention is to use the lowest ratio of ions, which would be one of each. By convention, the formula is MgO. The ionic compound NaCl is very common.

To balance the charges with the lowest number of ions possible, we need to have two chloride ions to balance the charge on the one magnesium ion.

Rather than write the formula MgClCl, we combine the two chloride ions and write it with a 2 subscript: MgCl 2. What is the formula MgCl 2 telling us? There are two chloride ions in the formula. Although chlorine as an element is a diatomic molecule, Cl 2 , elemental chlorine is not part of this ionic compound. The chlorine is in the form of a negatively charged ion , not the neutral element.

Write the proper ionic formula for each of the two given ions. Write the proper ionic formulas for each of the two given ions. Naming ionic compounds is simple: combine the name of the cation and the name of the anion, in both cases omitting the word ion. Do not use numerical prefixes if there is more than one ion necessary to balance the charges. NaCl is sodium chloride, a combination of the name of the cation sodium and the anion chloride. MgO is magnesium oxide. MgCl 2 is magnesium chloride— not magnesium dichloride.

In naming ionic compounds whose cations can have more than one possible charge, we must also include the charge, in parentheses and in roman numerals, as part of the name.

Again, no numerical prefixes appear in the name. The number of ions in the formula is dictated by the need to balance the positive and negative charges. How do you know whether a formula—and by extension, a name—is for a molecular compound or for an ionic compound? Molecular compounds form between nonmetals and nonmetals, while ionic compounds form between metals and nonmetals. The periodic table Figure 3.

There also exists a group of ions that contain more than one atom. These are called polyatomic ions. Only one of them, the ammonium ion, is a cation; the rest are anions. Most of them also contain oxygen atoms, so sometimes they are referred to as oxyanions. Some of them, such as nitrate and nitrite, and sulfate and sulfite, have very similar formulas and names, so care must be taken to get the formulas and names correct.

Note that the -ite polyatomic ion has one less oxygen atom in its formula than the -ate ion but with the same ionic charge. The naming of ionic compounds that contain polyatomic ions follows the same rules as the naming for other ionic compounds: simply combine the name of the cation and the name of the anion.

Do not use numerical prefixes in the name if there is more than one polyatomic ion; the only exception to this is if the name of the ion itself contains a numerical prefix, such as dichromate or triiodide. Working out the charges of ions The charge of many ions can be worked out using patterns in the periodic table. Reveal answer up. Silver I. Copper II.

Lead II. Iron II. Iron III. Hydroxide OH -. Carbon, which consists of 6 protons and 8 neutrons, is an unstable isotope produced the reaction of free neutrons produced from cosmic rays with nitrogen in the upper atmosphere. Carbon undergoes beta decay to produce nitrogen, with a half-life of years:. The amount of carbon thus produced is extremely small — approximately 7 kilograms per year — but small amounts of this carbon are taken up in the form of carbon dioxide along with the "normal" isotopes of carbon by green plants, and this isotope also becomes incorporated into the things that eat the green plants and also the things that eat the things that eat the green plants — and so on.

Once an organism dies, it stops taking in carbon or anything else, for that matter , and the carbon that it had at the moment of death decays, and is no longer replaced. By measuring the amount of carbon remaining in an organic sample, it is possible to determine how long ago the organism died.

This technique works for carbon-containing materials that are up to about 50, years old; beyond that, there is too little carbon remaining to get an accurate date, and some other form of radiometric dating must be used.

This technique was developed by Willard F. Libby in the s, who received the Nobel Prize in Chemistry in for this work. Silicon is a dark gray element with a metallic luster.

The name of the element is derived from the Latin word for flint, silicis. In the form of silica SiO 2 or one of the silicates SiO 4 4- , it is found in many different minerals, including clay, quartz, zircon, feldspar, mica, zeolites, aluminosilicates, sand, etc.

It is also found in the gemstones opal, agate, rhinestone, and amethyst. Silicon is one of the most important elements on the periodic table at least from the perspective of computers! Ultrapure silicon doped with boron or phosphorus is used as semiconductors in transistors, which are heavily employed in computers, solar panels, and other applications. Silica which is primarily silicon dioxide, SiO 2 , is used in the manufacture of glass.

Silicones, which consist of chains of alternating silicon and oxygen atoms, are used in oils, lubricants, and silicone rubber. Germanium is a hard, grayish white element with a metallic luster. The name of the element is derived from the Latin word for Germany, Germania.

It is found in the Earth's crust at a concentration of 2 ppm, making it the 52nd most abundant element. It is found in the ores argyrodite [Ag 8 GeS 6 ] and germanite [Cu 13 Fe 2 Ge 2 S 16 ], but is more frequently obtained as a by-product of the refining of zinc.

Like silicon, germanium is used as a semiconductor, and is widely used in the computer industry. The relatively large increase between tin and lead is due to the greater difficulty in removing the 6s 2 pair in lead than the corresponding 5s 2 pair in tin. Again, the values are all in kJ mol -1 , and the two charts are on approximately the same scale. These effects are due to the Theory of Relativity.

Heavier elements such as lead experience a relativistic contraction of the electrons that draws the electrons closer to the nucleus than expected.

Because they are closer, they are more difficult to remove. The heavier the element, the greater this effect becomes. This affects s electrons to a greater degree than p electrons. In lead, the relativistic contraction makes it energetically more difficult to remove the 6s electrons than expected. The energy releasing terms when ions are formed like lattice enthalpy or hydration enthalpy cannot compensate for this extra energy.

Carbon normally forms four covalent bonds rather than two. Using the electrons-in-boxes notation, the outer electronic structure of carbon looks like this:. There are only two unpaired electrons. Before carbon forms bonds, however, it normally promotes an s electron to the empty p orbital.