Atoms, Ions & Compounds Unit 3

Vocab Flash cards octet rule ion ionization energy electromagnetism Law of Multiple Proportions cationanion ionic bonds

Atomic Theory of Matter The theory that atoms are the fundamental building blocks of matter - John Dalton (early 1800’s).

Dalton’s Postulates All atoms of a given element are identical (same size, mass and other properties) but atoms of one element are different from the atoms of all other elements All atoms of a given element are identical (same size, mass and other properties) but atoms of one element are different from the atoms of all other elements Atoms are neither created nor destroyed in chemical reactions, simply rearranged. Atoms can not be changed into different atoms by chemical reactions. Atoms are neither created nor destroyed in chemical reactions, simply rearranged. Atoms can not be changed into different atoms by chemical reactions. Compounds are formed when atoms of more than one element combine; a given compound always has the same ratio of atoms. Compounds are formed when atoms of more than one element combine; a given compound always has the same ratio of atoms. Each element is composed of extremely small particles called atoms. Each element is composed of extremely small particles called atoms.

Daltons Atomic Theory explains three laws. The Law of Conservation of Mass. The Law of Constant Composition The Law of Multiple Proportions

Law of Constant Composition Joseph Proust (1754–1826) Also known as the law of definite proportions. The elemental composition of a pure substance never varies. Ex: H 2 O from Atlantic Ocean vs. Pacific Ocean Ex: H 2 O from Atlantic Ocean vs. Pacific Ocean

The Law of Multiple Proportions Two elements can be combined to form more than one compound. The ratio of the masses is a small whole number.

Law of Conservation of Mass The total mass of substances present at the end of a chemical process is the same as the mass of substances present before the process took place.

Octet Rule atoms tend to gain, lose or share electrons so as to have eight electrons in their outer electron shell try to achieve the same configuration as the nearest noble gas

Ions When atoms lose or gain electrons, they become ions. Cations are positive and are formed by elements on the left side of the periodic chart. Cations are positive and are formed by elements on the left side of the periodic chart. Anions are negative and are formed by elements on the right side of the periodic chart. Anions are negative and are formed by elements on the right side of the periodic chart.

An Na 1+ ion containing 11 protons and 12 neutrons would contain ___ electrons

Correct Answer: The +1 charge indicates there is 1 more proton than electrons: 11  1 =

Which of the following species has the greatest number of electrons? 1.Cl  Ca 2+ P 3  K Ar

Correct Answer: K has 19 electrons; all the other species listed have only 18 electrons. 1.Cl  Ca 2+ P 3  K Ar

Ionic Bonds Ionic compounds (such as NaCl) are generally formed between metals and nonmetals.

Ionization Energy The energy required to remove an electron from an atom First ionization energy is that energy required to remove first electron. First ionization energy is that energy required to remove first electron. Energy + X  X + + electron Second ionization energy is that energy required to remove second electron, etc. Second ionization energy is that energy required to remove second electron, etc. Energy + X  X +2 + electron

Ionization Energy It requires more energy to remove each successive electron. When all valence electrons have been removed, the ionization energy takes a quantum leap.

Trends in First Ionization Energies As one goes down a column, less energy is required to remove the first electron. the valence electrons are farther from the nucleus. the valence electrons are farther from the nucleus.

Electronegativity How strongly an atom attracts electrons Fluorine has the highest electronegativity with the strongest attraction for electrons Francium has the lowest electronegativity

Writing Formulas Because compounds are electrically neutral, one can determine the formula of a compound this way: The charge on the cation becomes the subscript on the anion. The charge on the cation becomes the subscript on the anion. The charge on the anion becomes the subscript on the cation. The charge on the anion becomes the subscript on the cation. If these subscripts are not in the lowest whole- number ratio, divide them by the greatest common factor. If these subscripts are not in the lowest whole- number ratio, divide them by the greatest common factor.

The compound, CuSO 4, is called 1.Calcium sulfide 2.Carbon sulfide 3.Calcium sulfite 4.Calcium sulfate 5.Copper sulfate

Correct Answer: The compound is ionic, derived from the copper(II) cation (Cu 2+ ) and the sulfate anion (SO 4 2  ). 1.Calcium sulfide 2.Carbon sulfide 3.Calcium sulfite 4.Calcium sulfate 5.Copper sulfate

The correct name for the compound, MgC 2 is 1.Carbon magneside 2.Magnesium carbide 3.Magnesium carbonate 4.Manganese dicarbide 5.Magnesium dicarbide

Correct Answer: In this unusual ionic compound, the cation is magnesium cation (Mg 2+ ) and the anion is carbide or acetylide (C 2 2  ). 1.Carbon magneside 2.Magnesium carbide 3.Magnesium carbonate 4.Manganese dicarbide 5.Magnesium dicarbide

The simplest chemical formula for the binary ionic compound Ca x N y is 1.Ca 2 N 2.Ca 2 N 3 3.Ca 3 N 2 4.Ca 3 N

Correct Answer: Ca loses two electrons to become Ca 2+, while N gains three electrons to become N 3 . To be neutral, positive charges and negative charges have to balance. 1.Ca 2 N 2.Ca 2 N 3 3.Ca 3 N 2 4.Ca 3 N