make a project atom and molecules in 4pages
Answers
It is the smallest constituent unit of matter that posses the properties of the chemical element. Atoms don’t exist independently, instead, they form ions and molecules which further combine in large numbers to form matter that we see, feel and touch.
Atoms are much too small to be seen; hence experiments to find out their structure and behavior have to be conducted with large numbers of them. From the results of these experiments we may attempt to construct a hypothetical model of an atom that behaves like the true atom.
Molecules consist of one or more atoms bound together by covalent (chemical) bonds. Atoms may be depicted by circle shapes, each of which has a nucleus at the center (containing protons and neutrons), surrounded by one or more concentric circles representing the ‘shells’ or ‘levels’ in which the electrons surrounding the nucleus of the atom are located and markings indicating the electron.at each level. A molecule is the smallest thing a substance can be divided into while remaining the same substance. It is made up of two or more atoms that are bound together by chemical bonding.
Particle nature, Basic units, Atoms and molecules, Law of constant proportions, Atomic and molecular masses.
Facts that Matter
• Law of Chemical Combination Given by Lavoisier and Joseph L. Proust as follows: (i) Law of conservation of mass: Mass can neither be created nor destroyed in a chemical reaction. e.g.,A+B-C+D Reactants R Products Mass of reactants = Mass of products (ii) Law of constant proportion: In a chemical substance the elements are always present in definite proportions by mass. E.g., in water, the ratio of the mass of hydrogen to the mass of oxygen is always 1 : 8 respectively. These laws lacked explanation. Hence, John Dalton gave his theory about the matter. He said that the smallest particle of matter is called ‘atom’.
• Dalton’s Atomic Theory 1. Every matter is made up of very small or tiny particles called atoms. 2. Atoms are not divisible and cannot be created or destroyed in a chemical reaction. 3. All atoms of a given element it are same in size, “mass and chemical properties. 4. Atoms of different elements are different in size, mass and chemical properties. 5. Atoms combine in the ratio of small whole number to form compounds. 6. The relative number and kinds of atoms are constant in a given compound. 9
• Atom Atoms are the smallest particles of an element which can take reaction. Size of an atom: Atomic radius is measured in nanometres. Atomic radii of hydrogen atom = 1 × 10–10 m.
• Molecule It is the smallest particle of an eleme4It- or a dolnpound which can wxist independently. • Molecules of an element constitutes same type of atoms. 1.w • Molecules may be monoatomic, di-atomic or polyatomic. IT . • Molecules of compounds join together in defmite proportionsrand constitutes different type of atoms.
• Atomicity The number of atoms constituting a Molecule is known as its atomicity.
• Ions The charged particles (atoms) are called ions, they charge or negative charge on it: Negatively charged ionis called anion (C1�). Positively charge ion is called cation (Na+).
• Valency The combining capacity of an element is known as its valency: Valency is used to fmd out how atom of an element will combine with the atom of another element to form a chemical compound. (Every atom want, to become stable, to do so it may loose, gain or share electrongs. (i) If an atom consists of 1, 2 or 3 electrons in its valgncesI ell then its valency is 1, 2 or 3 respectively, (ii) If an atom consists of 5, 6 or 7 electrons in the outermost shell, then it will gain 3, 2 or 1 electron respectively and its valency will be 3, 2 or 1 respectively. (ii) If an atom has 4 electrons in the outermost shell than it will she this electron and hence its valency will be 4. (iv) If an atom has 8 electrons in the outermost shell then its valency is 0.