Bonding And Tyoes Of Substance Flashcards
(32 cards)
What is an ion?
An ion is an atom or molecule that carries an overall electric charge because it has lost or gained electrons.
Positive ions are called cations; Negative ions are called anions.
How are positive and negative ions formed?
Positive ions (cations) form when an atom loses one or more electrons. Negative ions (anions) form when an atom gains one or more electrons.
How do you calculate the number of protons, neutrons, and electrons in an ion?
Protons = atomic number. Neutrons = mass number – atomic number. Electrons = atomic number (adjusted for charge):
• Positive ion → subtract electrons (e.g., Na⁺ → 11 – 1 = 10 electrons)
• Negative ion → add electrons (e.g., Cl⁻ → 17 + 1 = 18 electrons).
What are the charges on ions from Groups 1, 2, 6 and 7?
Group 1 → 1⁺ (loses 1 electron). Group 2 → 2⁺ (loses 2 electrons). Group 6 → 2⁻ (gains 2 electrons). Group 7 → 1⁻ (gains 1 electron).
How do you work out the formula of an ionic compound from the formulae of the ions it contains?
Balance the total positive and negative charges so they cancel out. Combine ions in the simplest ratio.
Example: Na⁺ and Cl⁻ → NaCl; Mg²⁺ and Cl⁻ → MgCl₂ (needs 2 Cl⁻ to balance Mg²⁺).
What do the endings –ide and –ate mean in ion names?
–ide → compound contains only 2 elements (e.g., sodium chloride). –ate → compound contains oxygen as well as other elements (e.g., sodium sulfate, NO₃⁻ nitrate).
What is ionic bonding?
Ionic bonding involves the transfer of electrons from a metal to a non-metal, forming oppositely charged ions which are strongly attracted by electrostatic forces.
Why do ions in ionic compounds usually have full outer shells?
Because during ionic bonding, atoms transfer electrons to obtain stable, full outer electron shells (like noble gases).
How do you represent ionic bonding using dot and cross diagrams?
Show electron transfer from metal to non-metal. Use dots and crosses to show electrons from each atom. Show charge on each ion after transfer (e.g., Na⁺, Cl⁻). Indicate full outer shells for ions. Enclose each ion in square brackets with charge outside.
How are ions arranged in an ionic compound?
Ions are held together in a giant ionic lattice, a regular repeating structure of alternating positive and negative ions, held by strong electrostatic forces in all directions.
Why do ionic compounds have high melting and boiling points?
Strong electrostatic forces between oppositely charged ions. A lot of energy is needed to overcome these forces and break the lattice.
Why do most ionic compounds dissolve easily in water?
Water molecules are polar, so they surround and separate ions, weakening the electrostatic forces and dissolving the compound.
Why can’t solid ionic compounds conduct electricity, but molten/dissolved ones can?
Solid → Ions are held in fixed positions → no mobile charge carriers. Molten/dissolved → Ions are free to move and carry electric current.
What is a covalent bond?
A covalent bond is a shared pair of electrons between two atoms.
How do non-metals form covalent bonds?
Non-metals share electrons with other non-metals to achieve full outer electron shells.
What are the ways to represent molecules (and pros/cons)?
Dot and cross diagrams: + Shows electron sharing clearly; - Doesn’t show shape of molecule. Displayed formula: + Shows bonds between atoms; - Doesn’t show lone pairs or 3D shape. Ball and stick models: + Shows 3D structure; - Misleading bond lengths and angles. 3D space-filling models: + Shows space occupied by atoms; - Hard to see bonds clearly.
How do simple molecules form?
Atoms join together by covalent bonds, forming small molecules (e.g., H₂, O₂, CO₂).
Why do simple molecules have low melting and boiling points?
Weak intermolecular forces between molecules. Little energy needed to overcome these forces (not the covalent bonds).
Why don’t simple molecular substances conduct electricity?
No free electrons or ions. Cannot carry an electric current.
What is a polymer?
Polymers are large molecules made of repeating units (monomers), joined by covalent bonds.
Example: poly(ethene).
What are giant covalent structures?
Solids made of a network of atoms covalently bonded in a continuous lattice (e.g., diamond, graphite, silicon dioxide).
Why do giant covalent structures have high melting points?
Many strong covalent bonds. Large amounts of energy needed to break the network.
Why don’t giant covalent structures usually conduct electricity?
No free electrons (except graphite). Electrons are tightly held in bonds.
Describe diamond’s structure and why it is hard.
Each carbon atom forms 4 covalent bonds → rigid tetrahedral lattice. Strong bonds throughout → very hard. Doesn’t conduct electricity (no free electrons).
