190 likes | 514 Views
Bohr-Rutherford Diagram. Bohr-Rutherford Diagram. Way to show the arrangement of electrons around the nucleus for the first 20 elements Nucleus holds the protons and neutrons, which we know from the atomic number The electrons are drawn on the orbits (rings) around the nucleus.
E N D
Bohr-Rutherford Diagram • Way to show the arrangement of electrons around the nucleus for the first 20 elements • Nucleus holds the protons and neutrons, which we know from the atomic number • The electrons are drawn on the orbits (rings) around the nucleus
There is a maximum number of electrons each orbit can hold • Excess electrons move to the next orbit around the nucleus • The first orbit holds 2 • The second and third orbit holds 8 • The fourth orbit holds 18
Examples Lets draw the Bohr Rutherford diagram of Potassium K Lets draw the Bohr-Rutherford diagram of fluorine F
Do you notice anything about the electrons on the outer-most orbit?
The electrons on the outer-most orbit are responsible for the reactivity of an atom • Atoms want their outer orbit full • The first orbit wants two electrons • The second and third want eight electrons • The fourth wants eighteen electrons
They fill their outer orbit by reacting with other elements • This explains why elements form compounds • Elements that have a full outer orbit are more stable
Ionic Compounds/Covalent Compounds • Ionic compounds - occurs between ions, which are negatively charged or positively charged ions • Atoms that don’t have a full outer orbit either give up electrons or take electrons to fill their shell giving them a positive or negative charge • Ionic compounds occur between metals and non-metals • Covalent compounds/molecular compounds - want to fill their outer shell but they share the electrons between atoms instead of losing or gaining electrons • There is no charge • Molecular compounds occur between non-metals and non-metals
Ions and Ionic Compounds • Look at Sodium and Chloride
You can look at the periodic table to determine whether an ion gives electrons or takes electrons • Ions have similar reactivity according to their group, i.e. Alkali Metals are likely to give up one electron, etc. • This tells us how many electrons the ion needs to give up or gain to have a full outer-shell; this is important when writing chemical formulas for ionic compounds
Chemical Formulas for Ionic Compounds • When writing the chemical formula of an ionic compound you don’t just write the ions; for example Na+ Cl-, it is written as NaCl • If we look at the ionic compound that involves Mg2+ and Cl1- Magnesium needs to give up 2 electrons to have a full outer shell, while Chlorine needs only 1 electron to have a full outer shell • Therefore, we need 2 chlorine atoms per magnesium ion to satisfy both ions
Therefore, the chemical formula for Mg2+ and Cl1- is MgCl2 • You can also figure out the chemical formula for an ionic compound by using the criss-cross method, and drop the charges • Mg2+ Cl1- = MgCl2 • Example write the chemical formula for Al3+ and O2-
Al2O3 • Some ions have multiple charges i.e. Iron (Fe) can either give up 3 electrons or 2 electrons depending on the ion it is bonding with • You can identify which ion is used in an ionic compound by looking at the chemical formula • For example if we look at Fe2O2
For example if we look at Fe2O2 • Using the criss-cross method you can identify which Fe ion was used • Fe2 O2 which becomes Fe2+ and O2- • You always reduce ionic compounds when writing their chemical formula, so Fe2O2 becomes FeO • Using the chemical formula Ni2S2 which Nickel ion is involved in this ionic compound.
Naming Ionic Compounds • Naming ionic compounds involves writing the metal first than the non-metal and changing the non-metals ending to “ide” • Ex. MgCl2 Magnesium Chloride • Name this ionic bond, Al2O3