Final answer:
Atoms bond in different ways, as seen in potassium fluoride (ionic bonding), water (covalent bonding), and boron trifluoride (covalent bonding with trigonal planar geometry).
Step-by-step explanation:
To explain how atoms bond together in different compounds using dot-cross diagrams, we'll look at potassium fluoride (KF), water (H2O), and boron trifluoride (BF3).
Potassium and Fluorine in Potassium Fluoride (KF)
In potassium fluoride, potassium (K) loses one electron to achieve a noble gas configuration, and this electron is gained by fluorine (F), which also attains a noble gas electron configuration. The electronegativity difference between potassium and fluorine is quite large (3.2), indicating an ionic bond. Potassium becomes a K+ ion, and fluorine becomes an F− ion.
Hydrogen and Oxygen in Water (H2O)
Water is formed by covalent bonding, where oxygen shares two pairs of electrons with two hydrogen atoms. Each hydrogen atom shares one electron to form a single covalent bond, which results in a bent molecular shape due to the two lone pairs of electrons on the oxygen atom.
Fluorine and Boron in Boron Trifluoride (BF3)
Boron trifluoride features boron bonding with three fluorine atoms through single covalent bonds to form a molecule with a trigonal planar geometry. Each fluorine atom provides one electron, and boron shares its three electrons to form the bonds, achieving a stable configuration, albeit with an incomplete octet on the boron.