Isotope The term isotope is formed from the Greek roots isos (equal) and topos (place). Hence: "the same place," meaning that different isotopes of a single element occupy the same position on the periodic table. The number of nucleons (protons and neutrons) in the nucleus is the mass number, and each isotope of a given element has a different mass number due to different number of neutrons.

Isotope Isotops of Hydrogen Nucleons Carbon Chlorine 1H 1 Proton 12C 6 Protons 6 Neutrons 35Cl 17 Protons 18Neutrons 2H 1 Neutron 13C 7 Neutrons 37Cl 20Neutrons 3H 2 Neutron 14C 8 Neutrons -

Isotopic Effect A neutral atom has the same number of electrons as protons. Thus, different isotopes of a given element all have the same number of protons and share a similar electronic structure. Because the chemical behavior of an atom is largely determined by its electronic structure, different isotopes exhibit nearly identical chemical behavior. However, heavier isotopes tend to react somewhat more slowly than lighter isotopes of the same element.

Space-Filling Model of Methane

Ball-and-Stick Model of Methane

Ball-and-Stick Models of the Ammonium Ion and the Nitrate Ion

Chemical Bonding The forces that hold atoms together in compounds are called chemical bonds. Covalent Bonds: One way that atoms can form bonds is by sharing electrons. These bonds are called covalent bonds, and the resulting collection of atoms is called a molecule. Molecules can be represented by chemical, For example, the formula for carbon dioxide is CO2, meaning that each molecule contains 1 atom of carbon and 2 atoms of oxygen. Examples of molecules that contain covalent bonds are hydrogen (H2), water (H2O),oxygen (O2), ammonia (NH3), and methane (CH4).

Ionic Bonds A second type of chemical bond results from attractions among ions. An ion is an atom or group of atoms that has a net positive or negative charge. Common table salt is or sodium chloride (NaCl) is example of ionic compound. Sodium (Na) losses one electron and remaining 10 electrons, now has a net 1 charge (Na+), it has become a positive ion. A positive ion is called a cation. The Chlorine atom gains one electron and 18 electrons produce a net 1 charge; the chlorine has become an ion with a negative charge—an anion (Cl─). The chloride ion is written as Cl, and the process is represented as;

Ionic Bonds Because anions and cations have opposite charges, they attract each other. This force of attraction between oppositely charged ions is called ionic bonding. So, they form NaCl. A solid consisting of oppositely charged ions is called an ionic solid. Ionic solids can consist of simple ions, as in sodium chloride, or of polyatomic (many atom) ions, as in ammonium nitrate (NH4NO3), which contains ammonium ions (NH4) and nitrate ions (NO3).

Question The element rhenium (Re) exists as two stable isotopes and 18 unstable isotopes. Rhenium-185 has in its nucleus a) 75 protons, 75 neutrons. b) 75 protons, 130 neutrons. c) 130 protons, 75 neutrons. d) 75 protons, 110 neutrons. e) not enough information is given.

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Question The numbers of protons, neutrons, and electrons in are: a) 20 p, 19 n, 19 e b) 20 p, 19 n, 20 e c) 19 p, 20 n, 20 e d) 19 p, 20 n, 19 e e) 19 p, 20 n, 18 e

Question An isotope, X, of a particular element has an atomic number of 7 and a mass number of 15. Therefore, a) X is an isotope of nitrogen. b) X has 8 neutrons per atom. c) X has an atomic mass of 14.0067. d) a and b e) a, b, and c

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Periodic Table Mendeleev’s Periodic Table Mendeleev (1869) arranged elements in the periodic table by their increasing mass numbers. • He left open spaces in his periodic table to account for elements not yet discovered. However, It was rejected due to some serious flaws.

Henry Moseley In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements*. He rearranged the elements in order of increasing atomic number. *“There is in the atom a fundamental quantity which increases by regular steps as we pass from each element to the next. This quantity can only be the charge on the central positive nucleus.” 1887 - 1915

Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties.

PERIODIC TABLE

Li, Be, B, C, N. O, F, Ne PERIODS The horizontal rows of the periodic table are called PERIODS. There are 7 periods in the periodic table. H Li Na K B Cs Fr GROUPS or FAMILIES The vertical columns of the periodic table are called GROUPS, or FAMILIES. The elements in any group of the periodic table have similar physical and chemical properties! There are 8 groups in the periodic table.

The Periodic Table Becomes Useful!! Elements in the same group have similar chemical and physical properties!! (Mendeleev did that on purpose.) Why?? They have the same number of valence electrons. They will form the same kinds of ions.

What is an ELEMENT? A substance composed of a single kind of atom. Cannot be broken down into another substance by chemical or physical means.

What is a COMPOUND? A substance in which two or more different elements are CHEMICALLY bonded together.

What is a MIXTURE? Two or more substances that are mixed together but are NOT chemically bonded.

Compounds Naming The most important rules for naming compounds other than organic compounds are given below; The systems for naming inorganic binary compounds (compounds composed of two elements) are classified into type-1. Binary Ionic Compounds (Type I) Binary ionic compounds contain a positive ion (cation) always written first in the formula and a negative ion (anion). In naming these compounds, the following rules apply:

Naming Type I Binary Compounds 1. The cation is always named first and the anion second. 2. A monatomic (meaning “one-atom”) cation takes its name from the name of the element. For example, Na is called sodium in the names of compounds containing this ion. 3. A monatomic anion is named by taking the root of the element name and adding -ide. Thus the Cl ion is called chloride.

Q. Name each binary compound. a. CsF b. AlCl3 c. LiH Solution: Type I Binary Compounds Q. Name each binary compound. a. CsF b. AlCl3 c. LiH Solution: a. CsF is cesium fluoride. b. AlCl3 is aluminum chloride. c. LiH is lithium hydride. Notice that, in each case, the cation is named first, and then the anion is named.

Binary Ionic Compounds (Type II) There are many metals that form more than one type of positive ion and thus form more than one type of ionic compound with a given anion. For example, the compound FeCl2 contains Fe+2 ions, and the compound FeCl3 contains Fe+3 ions. In a case such as this, the charge on the metal ion must be specified. The systematic names for these two iron compounds are iron (II) chloride and iron (III) chloride, respectively, where the Roman numeral indicates the charge of the cation.

Examples:

Binary Ionic Compounds (Type II) Another system for naming these ionic compounds that is seen in the older literature was used for metals that form only two ions. The ion with the higher charge has a name ending in -ic, and the one with the lower charge has a name ending in -ous. In this system, for example, Fe+3 is called the ferric ion, and Fe+2 is called the ferrous ion. The names for FeCl3 and FeCl2 are then ferric chloride and ferrous chloride, respectively.

Binary Covalent Compounds (Type III) Binary covalent compounds are formed between two nonmetals. Although these compounds do not contain ions, they are named very similarly to binary ionic compounds. Naming Binary Covalent Compounds The first element in the formula is named first, using the full element name. 2. The second element is named as if it were an anion. 3. The prefix mono- is never used for naming the first element. For example, CO is called carbon monoxide, not monocarbon monoxide.

Examples:

Acids When dissolved in water, certain molecules produce a solution containing free H+ ions (protons). An acid is a molecule in which one or more H + ions are attached to an anion. The rules for naming acids depend on whether the anion contains oxygen. If the name of the anion ends in -ide, the acid is named with the prefix hydro- and the suffix -ic. For example, when gaseous HCl is dissolved in water, it forms hydrochloric acid. When the anion contains oxygen, the acidic name is formed from the root name of the anion with a suffix of -ic or -ous, depending on the name of the anion

Question Name the following compounds: 1) Al2(SO4)3 2) NH4NO3 3) NaH 4) K2Cr2O7 5) AgCl 6) CaSO4 7) N2O3

Question Name the following compounds: 1) iron (III) oxide 2) dinitrogen trioxide 3) aluminum hydroxide 4) sulfurous acid 5) phosphoric acid 6) carbon tetrachloride 7) tin(II) iodide