The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:
The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:
Introduction
What is an atom?
Atom is the smallest component in which matter may be separated without the release of electrically charged particles. It is also the smallest unit of matter with the characteristic properties of a chemical substance. The atom is the fundamental building block for chemistry. Atoms are hollow spaces. This space consists of a positively charged nucleus of protons and neutrons covered by a cloud of negatively charged electrons.
Atoms are made up of three basic particle types:
Neutrons and protons have approximately the same mass, and the mass of an electron is negligible in comparison to that. A proton carries a positive charge, there is no charge for a neutron and an electron is charged negatively. An atom contains an equal number of protons and electrons, so an atom has no charge overall. An atom’s nucleus contains only protons and neutrons and is therefore positively charged. The electrons occupy the spatial region around the nucleus. Most of the mass is, therefore, concentrated within the nucleus.
The size of an atom is extremely small, enough smaller than what we imagine. When more than a million atoms are accumulated together, a film of an atom as thick as a slim sheet of paper is created. The size of a detached atom is difficult to measure because the locations of electrons enclosing the nucleus are hard to locate. Avogadro’s Law helps in defining atomic size.
However, by considering that the distance between adjacent atoms is equivalent to half the radius of an atom, the size of an atom can be determined. In general, the atomic radius is estimated in nanometers.
1 m = 10^9nm
In a chemical element, atomic weight is the mass of an atom. It is roughly equivalent to the total atomic neutrons and protons. It is expressed in units of atomic mass (denoted by u). The molar mass of 1 atom of C-12 is equal to exactly one-twelfth and the relative atomic masses of elements are determined with respect to-12 atoms.
A molecule is defined as the smallest unit of a compound containing the compound’s chemical properties. Molecules are composed of atomic groups.
Mole Concept
The mole concept is a formula which helps us calculate the number of atoms or molecules. The formula is:
Number of Atoms or Molecules = (Number of Moles)*(6.022*1023)
The Forces between Atoms and Molecules
The simplest forces between atoms are those that occur as a consequence of the movement of electrons. A basic example is that of sodium fluoride. The sodium atom has a nuclear load of +11, with 2 electrons in the K shell, 8 in the L shell and 1 in the M shell. The nuclear charge of the fluorine atom is 9 with 2 electrons in the K shell and 7 in the L shell.
The outermost electron of the sodium atom can be quickly moved to the fluorine atom; all atoms then have a full shell, but sodium has a net charge of +1 and fluorine a net charge of-1. As a consequence, these ions attract each other by direct coulombic contact. The force between them is high and differs as x-2, where x is the distance between the ions, and it works in the direction of the line connecting the ions.
Moreover, it is unsaturated – one positive ion will draw multiple negative ions around it, and the force exerted by the positive ion on each negative ion is not influenced by the influence of other negative ions. Of addition, negative ions will repel each other as well.
Laws of chemical combination constitutes of:
Law of Conservation of Mass
In basic words, this law specifies that the matter cannot be created or destroyed. In other terms, the overall mass, that is, the sum of the reaction mixture mass and the products produced, stays unchanged. Antoine Lavoisier adopted this law in 1789 on the basis of the evidence he collected following close analysis of various combustion reactions.
Gay Lussac’s Law of Gaseous Volumes
Gay Lussac gave this law in 1808 on the basis of his findings. This law provides that when gases are generated or mixed in a chemical reaction, they do so in a simple volume ratio, provided that all gases are at the same temperature and pressure. This law can be viewed as another type of law of definite proportions. The main distinction between these two rules of chemical mixture is that the rule of Gay Lussac is laid out in terms of volume, whereas the law of some proportions is set out in terms of mass.
Avogadro’s Law Molar Mass
This law was proposed by Avogadro in 1811. It claimed that under the same conditions of temperature and pressure, the equal amount of all gases comprises an equal number of molecules. This ensures that 2 litres of hydrogen would contain the same amount of molecules as 2 litres of oxygen, since all gases are at the same temperature and pressure.
Law of Multiple Proportions
It states that as two components join to create more than one compound, the weights of one element, which combine with the defined weight of the other, are in the ratio of small whole numbers.
1. Define the atomic mass unit.
The atomic unit of mass is exactly described as 1/12 the mass of the carbon-12 atom. The carbon-12 atom holds six neutrons and six protons in its nucleus. The mass of the atomic unit is symbolized as AMU or AMU.
1 AMU = Average rest mass of the proton and rest mass of the neutron.
1 AMU = 1.67377 x 10-27 kilogrammes or 1.67377 x 10-24 grammes.
This chapter taught us the basics of atoms and molecules. We learned important concepts like atomic mass and size which will help in understanding Gay Lussac’s law of gaseous volumes and law of multiple proportions.
1. What is the difference between atoms and molecules?
Atoms are regarded as the ‘primary building blocks of matter.’ The smallest constituent unit of the substance is the characteristics of the chemical element. One or more atoms connected by covalent (chemical) bonds are made up of molecules.
2. What are the 4 types of atoms?
3. How many atoms are in a molecule?
Two atoms
Molecule: a group of two or more atoms that are held together by chemical bonds. Therefore, to form a molecule, at least 2 atoms are required.
4. What is bigger: atom or molecule?
Atoms are smaller than molecules and are the smallest building blocks of matter as well. When two or more atoms bond, they form molecules.
5. Can an atom be created?
It is impossible to create or destroy atoms, and they are indestructible; it is possible to break them into smaller parts. This was based on the law of conservation of mass.
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