Presentation on theme: "Ionic Bonding and Ionic Compounds. Atoms and Ions Atoms are the building blocks of matter (solids, liquids and gases). For example: Copper wire."— Presentation transcript:
Atoms and Ions Atoms are the building blocks of matter (solids, liquids and gases). For example: Copper wire is made of copper atoms. Diamond is made of carbon atoms. Oxygen gas is made of oxygen atoms. Atoms have a negatively charged particle called electrons that spin around their nucleus. Atoms are neutral because the protons equal the electrons.
How do Ions form? Ions are atoms with charges (+ or -). Some atoms have a tendency to either lose or gain electrons. They do this to become stable, that is, to have a fully filled valence shell. When atoms lose/gain e’s, they become ions. When ions attract to each other, they form ionic compounds via a chemical bond known as ionic bonding. Ionic compounds are neutral compounds.
Example 1: Sodium ion Sodium atom (11 e’s) has the electron configuration (2,8,1). The 3 rd electron shell has a capacity for a maximum of 8 e’s. However, in this case, there is only 1 valence electron. Hence, sodium atom is unstable. It is easier for sodium atom to lose 1 e than to gain another 7e’s Thus, sodium atom loses that 1 e It now has one less electron (but protons remain unchanged)
Example 2: Chloride ion Chlorine atom (_____e’s) has the electron configuration (_______). The 3 rd electron shell has a capacity for a maximum of 8 e’s. However, in this case, there _________ valence electrons. Hence, chlorine atom is _____________ as it is partially filled. It is easier for chlorine atom to lose/gain _____ an electron than to lose/gain _____ e’s Thus, chlorine atom loses/gains ____ e It now has one _____ electron (but protons remain unchanged)
Ionic Bonding Is a bond formed between positive and negative ions as a result of electrostatic attraction between them. Electrostatic force is the attraction of positive and negative particles. Positive ions are called cations. Metals lose electrons to form cations. Negative ions are called anions. Non-metals gain electrons to form anions.
Properties of Ionic Compounds Are hard, brittle crystalline solids at room temperature. Have high melting points. EXPLANATION The positive and negative ions are held together by strong electrostatic attraction in a 3-Dimensional network lattice. Hence they are strong and also large amounts of heat energy is needed to break its bonds (change the solid into liquid – melting process). Good conductors of electricity in molten form and in solution form but not in solid state. EXPLANATION This is because in melted/dissolved, the ions are free to move and carry electric current but in solid state, the ions are fixed position.
Example of An Ionic Compound - NaCl Has a melting point of 800°C Hard, brittle crystalline solid Positive and negative ions (Na+ and Cl-) are tightly packed and arranged in a 3- dimensional network lattice. Each ion is surrounded by 6 oppositely charged ions via strong electrostatic attraction. When dissolved in water or melted, the ions dissociate and are free to move and hence conduct electricity (able to carry electric current) Diagram of NaCl A look within
Work Set Text Questions Page 78 Numbers 9-10, 12 Page 81 Numbers 13-16 Page 82 Numbers 17-18 Page 85 Numbers 20, 21 Page 86 Number 22
Naming and Writing formula of Ionic Compounds Cations (positive ions) are written first followed by anion (negative ions). Ionic compounds are neutral substances. Hence the charges on cations and anions cancel each other. The formula is just shows a ratio of ions bonding – it is not the whole molecule – there is more ions than what is shown by the formula. Deriving formula of ionic compounds uses the “cross-over method”
How to Name and Derive Formulae? EXAMPLE Youtube videos…. http://www.youtube.com/watch?v=URc75hoKGLY http://www.youtube.com/watch?v=URc75hoKGLY http://www.youtube.com/watch?v=p9iQ5Qn42DM http://www.youtube.com/watch?v=p9iQ5Qn42DM
Task Naming Hydrated Compounds Text, page 85,86 Summarise in no more than 5 lines Give 5 examples – names and their formula