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Acids and Bases - pH

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Periodic classification of Elements

Dobereiner’s triads: According to Dobereiner’s triads – ‘when three elements in a triad are arranged in order of increasing atomic masses, the atomic mass of the middle element is roughly the average of the atoms of the other two elements.’ E.g. Li (6.9), Na (23), K (39). Avg at mass of Na = (6.9+39)/2 = 22.95. Limitations of Dobereiner’s triads: Dobereiner could identify only three triads from the elements known at that time. So, all the elements could not be arranged in triads. Newlands’ Law of octaves: According to the Newlands’ Law of octaves – when the elements are arranged according to increasing atomic mass, the properties of every eighth element are similar to that of first. E.g. elements with atomic mass up to 40 are H F Cl Li Na K Be Mg Ca B Al C Si N P O S Limitations of Newlands’ Law of octaves: This law was applicable only to lighter element...

Electron Affinity

Electron affinity is, essentially the opposite of the ionization energy: Instead of removing an electron from the element we add an electron to the element to create an anion. M + e- ----> M- E.A. Generally, the energy that results from this process (the electron affinity) is negative or close to zero. The more negative this energy the more this process is favored. The noble gases, alkali metals and alkali earth metals have E.A. close to zero - indicating that these groups of elements do not particularly like to become anions. However, the nonmetals and especially the halogens are highly negative and thus readily become anions. A periodic trend is evident, as was the case for the ionization energy. More.. Source: www.iun.edu/

What is Matter?

Matter is everything around you. Matter is anything made of atoms and molecules. Matter is anything that has mass and takes up space. Note that, mass is the amount of stuff in an object. Even though matter can be found all over the Universe, you only find it in a few forms. Scientists have identified five physical states of matter. Each of those states is sometimes called a phase . 1. Solids 2. Liquids 3. Gases 4. Plasmas and one state called 5. The Bose-Einstein condensate (BEC).

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