Extra Question Chapter 1:Chemical Reaction And Equations
Extra Question II Chapter 1:Chemical Reaction And Equations
Extra Question Chapter 2:Acid Ans Base
Important Question Chapter 3:Metal and Non Metal
Chapter 4:Carbon And Its Compoundl
Chapter 5:Periodic Classification of elememt
Chapter 7:Control and coordination
Chapter 8:How Do Organisms Reproduce?
Chapter 9:Hearedity And Evolution
Chapter 10:Light Reflection and Refraction
Chapter 11:The Human Eye and Colorful World
The modern periodic table arranges the elements in order of increasing atomic number. This pattern brings objects with similar characteristics into a vertical group and exhibits periodic repetition of similar characteristics
Mendeleev’s periodic table was important because it classified well-known elements based on their atomic size and chemical properties. He left differences for yet undiscovered objects and predicted their nature, many of which were later found to be surprisingly accurate when those objects were discovered
The reason for periodicity in the nature of elements is the repetition pattern in the outermost shell electron structure as we move from one element to another in periods and this causes repetition in chemical sus at regular intervals or times.
As we move through the period from left to right, the metallic color decreases. This is due to increased nuclear energy attracting electrons closer to each other, reducing the tendency to lose electrons. As we move down the group, the metallic collar increases. Due to the increase in the number of shells, the outermost electrons are further away from the nucleus, they can be lost more easily, which is characteristic of metals
As we move from left to right in the period, atomic mass decreases due to increased atomic energy attracting electrons closer to the nucleus but as we move down the cluster the atomic mass increases as shell mass increases and the outermost electrons are far from the nucleus
Isotopes are atoms of the same element with the same number of atoms but different masses. They have the same number of protons but different numbers of neutrons. For example, 1H, 2H (Deuterium), and 3H (Tritium) are isotopes of hydrogen. However, even strings are composed of atoms of the same size but with different atomic numbers. They have the same number of nuclei (protons + neutrons) but different numbers of protons. For example, 18Ar40 and 20Ca40 are isobaric.
A valence electron is the outermost electron of an atom. These electrons are important because they are involved in chemical reactions and bond formation. The number of valence electrons determines the chemical composition of an element
As you move from left to right at different periods in the periodic table the number of valence electrons increases from 1 to 8. This does not include transition metals with electron configurations
Higher gases are ineffective because their outermost electron shells are full, containing about eight electrons. This stable electronic structure means that there is no need to gain, lose or share electrons, so they are generally not involved in chemical reactions.
Transition factors are factors in groups 3-12 of the periodic table. They are characterized by a partially filled d orbital, multiple oxidation states, and generally stable ions. They include metals such as iron, copper and silver.
Generally, metals are lustrous, conduct heat and electricity well, ductile, malleable, lose electrons during chemical reactions Nonmetals tend to be thermally and electrically negative, do not luminesce, gain or share electrons when medicine is working .
Elements known as alkali metals in group 1 of the periodic table have one valence electron. They do a great job, especially with water, and are excellent conductors of thermal electricity. It is soft and can be cut with a knife.
As you move from left to right in the period, the material changes from metallic to non-metallic. The reactivity of the elements first decreases from Group 1 to Group 4, then increases from Group 4 to Group 7. Group 0 elements, noble gases, tend to be inert due to the overall electron shell outer shell so
The octet rule states that atoms must gain, lose, or share electrons in order to have a complete outer shell of eight electrons. This gives them stability. This rule applies to many things but there are many exceptions, especially for heavier items.
In general, electronegativity increases as you move from left to right due to increased atomic energy. In general, as atomic size increases, the in-group gradient decreases.
Hydrogen is unique in that it can be classified in Group 1 due to valence electrons similar to alkali metals, or classified in Group 17 because it can gain electrons to achieve complete outer shells like halogen but is usually placed in Group 1 .
The elements of group 17 of the periodic table, called halogens, have seven valence electrons. They are highly reactive nonmetals and usually exist as diatomic molecules. One more electron is needed to reach the entire outer shell.
Group 18 of the periodic table, contains a complete electron shell of outer layers of elements known as noble gases. This makes them very stable and unresponsive. They exist as monoatomic gases and have low boiling points
Lanthanides and actinides are two series that are usually placed at the bottom of the periodic table. Lanthanides (atomic numbers 57-71) resemble group 2 elements. Actinides (atomic numbers 89-103) are all radioactive
Ionization energy is the energy needed to remove an electron from an atom. Generally it increases (by increasing atomic energy) as you move through the period from left to right and decreases (by increasing atomic size) as you go down a group