atomic structure

• Atoms can gain or lose electrons to form negatively charged ions (anions) or positively charged ions (cations).
• The number of protons is equal to the number of electrons, so atoms are electrically neutral.
• The number of protons is equal to the number of electrons, so atoms are electrically neutral.
• Atom is the smallest unit consisting the universe.

  They can't be broken down my chemical means.
• Element is a group of atoms with the same number of protons.
• Isotope is an atoms of the same element/number of protons with different number of neutrons.
• Compound is two or more different elements chemically bonded together.
• I2, F2, Cl2 are diatomic molecules which isn't a compound!
• Mixture is two or more substances placed in the same container without chemical bonds.
• Homogenous: same state
• Heterogenous: different state
• Proton determines the element of an atom.
• Neutron determines the mass of an atom.
• Electron determines the chemical properties of an atom.
• Ionic compounds are bonded with ionic bonding which is an electrostatic attraction between oppositely charged ions.
• Ionic compounds have an ionic lattice structure which is a regular arrangement of alternating oppositely charged ions.
• Ionic compounds are brittle, easily breaks. E.g. crystals break when force is applied
• Ionic compounds are soluble in water because the ions are free to move around in the water.
• Ionic compound's electric conductivity is poor in solid, but good in liquid(molten) or aqueous.
• Ionic compounds have a high melting and boiling point.
• Metallic compounds have a metallic bonding which is a strong electrostatic attraction between positive metal ions and sea of delocalised electrons.
• Metallic compounds have a structure of metal atoms bonded to delocalised electrons.
• Metallic compounds are malleable which means they can be hammered into thin sheets (compression).
• Metallic compounds are ductile, which means they can be stretched (tension).
• Layers of metal cations can slide over each other.
• Alloys are mixture of two or more metals. Differently sized metal cations make it move difficult for layers to slide past each other.
• Examples of alloys: Steel (Fe + C), bronze (Cu + Sn), brass (Cu + Zn), and stainless steel(Steel + Cr).
• Metallic compounds are good conductor of electricity because the delocalised electrons can move freely and carry charge.
• Metallic compounds have a high melting and boiling point, they are stronger and denser than ionic compounds.
• Covalent compounds have a covalent bonding, which is a shared pair of electrons between atoms.
• Covalent compounds have a simple molecular or giant covalent structure.
• Covalent compounds have a low melting and boiling point since the intermolecular force is relatively weaker than the intermolecular forces in ionic/covalent/metallic compounds.
• Covalent compounds are poor conductor of electricity and they are insoluble.
• Giant covalent structures include diamond, graphite, silicon dioxide, and silicon carbide.
• Diamond is giant covalent structures with strong covalent bonds and a high melting and boiling point. 4 carbon atoms are bonded to each carbon atom. They are tetrahedral structure and poor electric conductor due to no moving charged particles.
• Graphite is made up of 3 carbon atoms covalently bonded to each carbon. They are trigonal planar and is soft. The layers of graphite can easily slide past each other. Used for pencil, lubricant. They have very high MP/BP and is a good conductor of electricity due to delocalised electrons.
• C60 fullerene is a molecule that is made up of 60 carbon atoms arranged in a hollow sphere. 3 carbon atoms per each carbon atom, trigonal, macromolecular structure. Relatively lower MP/BP than diamond/graphite. Poor conductor of electricity.
• Silicon dioxide (SiO2) has 4 oxygen atoms bonded to each Si, 2 silicon atoms bonded to each O. E.g. glass, soil, rocks, sand. Poor conductor of electricity due to the strong covalent bonds between the Si and O atoms. Very high MP/BP, and hard.