chemical bonds Flashcards
what is an atom
- electricity neutral
- eqal number of protons and electrons
what is an ion
- charged atom
- produced when atom lose or gain electrons
- unequal number of protons and electrons
what is a cation
metal atoms that have lost electrons to become positively charged (more protons than electrons)
what is an anion
- non-metal atoms that have gained electrons to become negatively charged (more electrons that protons)
how are ionic compounds formed
ionic compounds form when a cation and an anion join together by an ionic bond
what is a polyatomic ion
- ionic compounds can contain ions consisting of groups of atoms rather than a single atom
properties of ionic compounds
-all ionic compounds form lattices and crystals when solid
- ioinic formula is the simplest ration of the number of ions. ionic compounds do NOT form discrete molecules
-when solid the do not conduct electricity
- dissolved and molten- do conduct electricity (because the lattic breaks up and the ions (charged particles) are free to move)
-ionic compounds are brittle - they shatter when they are hit
what is covalent bonding
a covalent bond = a pair of shared electrons
sometimes two atoms share more than one pair of electrons
when does covalent bonding occur
covalent bonding forms when non-metal atoms share electrons to fill up their outer shell
what is a small covalent structure
-simple covalent structures have just a few atoms joined together - small discrete molecules
-can be gases, liquids or solids
-low melting and boiling points
giant covalent structures
-sometimes millions of atoms are joined together by covalent bonds
-this produces a rigid 3Dnetwork called a giant lattice. a diamond is a 3D network solid
what are different arrangements of the same atom called
allotropes
what is metallic bonding
-atoms of metals are tightly packed together in a giant lattice
-the outer electrons separate from their atoms and become delocalized creating a ‘sea of electrons’. the atoms become positive ions and are attracted to the electrons
-this attraction is called metallic bonding and is the reason why the positive metal ions do not repel each other
ionic bonding
metal + nonmetal
covalent bonding
nonmetal + nonmetal
