جميع المواضيع المتعلقة بـ ‘energy’

 

Electron affinity

Electron affinity

It is the amount of energy given out when an electron is added to a neutral gaseous atom. This results in the formation of an anion.

For example Cl + e– → Cl + energy. The electron affinity of chlorine is 348 kJ mol-1.

Electron affinity changes across a period. The electron affinity of the atoms increases from left to right along a period…

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Ionization energy

Ionization energy

(or potential) of an element is defined as “The amount of energy required or needed to remove an electron from the neutral gaseous atom to form unipositive ion , for example Na → Na+ + e– + energy

This is measured in electron volts per atom or kJ mol-1. For example IE of Na is 495 kJ mol-1.

Trends in ionization energy of elements.

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Quantization

Quantization: means that a quantity does not vary continuously. The energy of an electron in an atom cannot have any arbitrary value but only certain characteristic values. ­A definite quantum of energy is accepted while moving from lower to higher energy level or lost while moving from higher to lower energy level, It does not accept any amount of energy nor does it lose energy continuously.

Quantum of…

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adiabatic demagnetization

A technique for cooling a paramagnetic salt, such as potassium chrome alum, to a temperature near absolute zero. The salt is placed between the poles of an electromagnet and the heat produced during magnetization is re­moved by liquid helium. The salt is then isolated thermally from the sur­roundings and the field is switched off; the salt is demagnetized adiabati­cally and its temperature falls. This is because the demagnetized…

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CHEMICAL ENERGETICS

Internal energy: The energy stored in a fixed amount of a substance (atom or molecule) is known as its internal energy. It is denoted by the sign E.

Change in internal energy: It is the difference in the internal energies of the product and the reactant species taking part in a chemical reaction at constant volume. It is denoted by ΔE.

ΔE = Ep – Er

Where,     …

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Energy levels and sub-levels

Not all the electrons in an atom are located the same distance from the nucleus. Electrons reside in regions of space called shells, or principal energy levels, which are identified with numbers called principal quantum numbers. The number of electrons that can exist in each energy level is limited.

The maximum number of electrons for a specific energy is equal to 2n2, where n is the number of the…

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Atomic Spectrum of Hydrogen

when an electrical discharge is passed through a sample of hydrogen gas at low pressure, a pinkish glow is observed. This glow can be examined using a simple spectroscope. A number of separate lines can be observed. It is important to realize that each line in the spectrum corresponds to an electron’s changing from one energy level to another.

When electrical discharge is passed through hydrogen gas, energy is…

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Atomic Theory

Dalton’s Model of the atom. It is the basis of our understanding of the nature of matter. The following four statements comprise Dalton’s Model:

a –  All matter is made up of extremely tiny. particles. called atoms.

b-  Atoms are indivisible.

c – Atoms of the same element are alike.

d –  Atoms of different elements are different.

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Energy

Like matter, energy can be classified in different ways. For example, energy can either be kinetic or potential.

Kinetic energy is energy of motion. Gases are made of molecules that have more kinetic energy than molecules in the solid phase of that substance. For example, water molecules in steam have greater kinetic energy than molecules in liquid water.

Potential energy is energy…

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طاقة كيميائية

طاقة كيميائية chemical energy :

تسمى الطاقة المحتجزة في الروابط التساهمية بين الذرات باسم الطاقة الكيميائية . كل رابطة لها مقدار معين من الطاقة . و لكسر تلك الرابطة فإن يتطلب وجود طاقة لذلك في تفاعل يعرف باسم تفاعل ماص للحرارة ، و الروابط المكسرة ترتبط مع بعضها البعض مرة ثانية لتكون جزيئات جديدة محررة طاقة و في تفاعل يعرف باسم تفاعل طارد للحرارة. فإذا كانت الحرارة الكلية…

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