Matter and the Atomic Structure

Structure Question 3:The table below shows the melting and boiling points of three different substances. Substance Melting Point Boiling Point H -120°C -5°C I 45°C 98°C J 10°C 350°C Answer: What is the physical state of H, I and J at room temperature (25°C)?H: gaseous I: solid J: liquid Which substance diffuses the fastest at … Read more

Structure Question 2: An experiment is conducted to study the change of state of iodine. Some powder of solid iodine is heated as shown in the Figure above, the black solid iodine changes into a purple gas at 125°C. The purple gas is then cooled by a round bottom flask that fill with ice. Answer: … Read more

Structure Question 1: The above diagram shows the apparatus used in an experiment to determine the freezing point of liquid naphthalene. The liquid naphthalene is cooled from 100°C in a conical flask and it is stirred continuously with a thermometer. The temperature of liquid naphthalene is recorded in every 30 seconds. The results obtained are … Read more

Which of the following substances sublimes at room pressure when heated? Iodine Dry ice (Solid carbon dioxide) Naphthalene Ammonium Chloride Which of the following take place when water solidifies to become ice? Energy is absorbed from the surrounding. Water molecules get nearer to each other. Water molecules are not arranged orderly. The mass increase.

Valence Electron Valence electrons are the electrons in the outermost shell. The electrons in the outermost shell of an atom are called valence electrons. The valence electrons have great significance in determining the chemical properties of an atom. Elements with the same number of valence electron have the same chemical properties.   Example: Given that … Read more

We have learnt that electrons occupy orbits with definite energy level of an atom, as suggested by Neils Bohr. These orbits with definite energy level are known as the shell. Every single shell is capable of holding up to certain amount of electrons. The first shell can hold up to two electrons. This is called … Read more

Isotopes Isotopes are atoms of certain elements which have the same number of protons but different number of neutrons in the nucleus of the atoms. It can also be defined as atoms of certain elements with the same proton numbers but with different nucleon numbers. Properties of Isotope Number of proton equal Number of neutron … Read more

Proton Number and Nucleon Number Proton number = the number of protons Nucleon number = Number of protons + Number of neutrons Proton Number The proton number (Z) represent the number of protons found in the nucleus of an atom. Proton number = the number of protons The proton number is also known as the … Read more

The Charge of Particles A neutral atom contains the same number of electrons as the protons. The positive and negative charges of the protons and electrons respectively neutralise each other, for example, (+4) + (-4) = 0 If the number of protons is greater than the number of electrons, the particle is positively charged. If … Read more

Modern Atomic Model According to the modern atomic model, The central nucleus consists of protons and neutrons. It containing almost all the mass of the atom. the nucleus of an atom is very small compared to the size of the atom the electrons are orbiting outside the nucleus in the electron shells the electrons are … Read more