Chemistry: Atom and Electrons Essay examples

Submitted By Gowsika
Words: 817
Pages: 4

Chemistry Review Assignment:

1. Chemistry is the study of matter. 2. An atom is the basic unit of a chemical element. The atom is composed of very small nucleus. It is made of positively charged protons and neutron which have no charge. 3. All atoms of the same element are the same because of the atomic number. The atomic number of an element is equal to the number of protons in the nucleus of an atom or electrons. For the atom to achieve neutrality these two must be equal. 4. Atoms of different element are different because each element has different number of protons, neutrons and electrons. This is why they have different atomic number and properties. 5. An element is a substance that is made of only one type of atom; all of these atoms have the same atomic number. You can find the entire elements on the Periodic Table. 6. The element I have chosen from the periodic table is oxygen. Oxygen’s atomic number is 8 and its mass number is 16. Humans, animals and plants need oxygen for respiration. 7. Humans are mostly composed of carbon, oxygen, hydrogen and nitrogen. 8. The atoms of the same element can be different in the number neutrons in their nuclei. These atoms are called isotopes. 9. The atom carbon-14 there is 6 protons, 6 electrons and 6 neutrons. 10. The element is Lithium. No this element is not the same as Carbon-14 but both element are isotopes. 11. Sodium = Na + Chloride = Cl (when combined together makes a compound) NaCl (Sodium Chloride). A compound contains atoms of different elements which are chemically combined together. A compound had different element in a fixed ratio. It is arranged in a defined manner through chemical bonds. Whereas element are knows by their atomic number. 12. Energy levels are the distance of energy content from the electrons. The energy levels occupy sublevels in the order of increasing energy. 13. Electrons can move from one energy level to the next. The atom must gain or lose the right amount of energy. The higher an electron is in energy, the farther it is from the nucleus. 14. Sodium has 11 electrons. It has an atomic number of 11, so it has 11 protons. It has an atomic mass of 23, so it has 12 neutrons (23-11=12). Each element is in a neutral state so it will be a neutral atom, so it will have 11 electrons to neutralize the 11 protons. 15. All of the energy levels do not hold the same number of electrons. The first energy level can hold up to 2 electrons. The second energy level can hold up to 8 electrons and the third can hold up to 18 electrons. 16. The valence energy level is the outermost energy level. 17. Lithium has one electron in the valence energy level. It is not a stable electron and it will need to bond with another electron to be stable.

18. Electron shell diagram: Chlorine Atom. There are seven electrons in the valence energy level. The atom chlorine gains or shares electrons because it has 1