6.1 Chemical bonds Flashcards
define molecule
a group of 2 or more atoms joined together
define covalent bond
a bond made when a pair of electrons is shared by 2 atoms
define dot-and-cross diagram
a diagram used to show a covalent bond between atoms in a molecule. Electrons are represented by dots or crosses
define ion
an atom which has gained at least one electron to be negatively charged or lost at least one electron to be positively charged
define ionic bond
an attraction between a positively charged ion and a negatively charges ion
explain why oxygen had the formula O2 and water has the formula H2O
Oxygen is represented as O2 because oxygen molecules typically exist in pairs. Water is defined as H2O because a water molecule has two hydrogen atoms covalently bonded to a single oxygen atom.
“Only compounds are made up of molecules.”
Explain why this statement is wrong
Because molecules can be made with 2 atoms of the same element. (e.g. oxygen, hydrogen)
why is oxygen known as a ‘diatomic molecule’
because it exists as 2 atoms
why do sodium atoms have no overall charge?
because it has the same number of protons and electrons.
when sodium reacts with chlorine, ions are formed. Why?
Sodium and chloride form an ionic bond. An electron is transferred from the sodium atom to the chloride atom and so both atoms become ionic and have a full outer shell.
Draw a diagram to show what happens when a magnesium atom reacts with an oxygen atom to form magnesium oxide (MgO). What are the charges on each ion?
What is a cation?
positively charged ion (e.g Na +)
What is an anion?
negatively charged ion (e.g Cl - )