combination of three nuclei and ten electrons possesses special properties that make it unique among the more than 15 million chemical species we presently know. When we stop to ponder the consequences of this‚ chemistry moves from being an arcane science to a voyage of wonder and pleasure as we learn to relate the microscopic world of the atom to the greater world in which we all live. The molecule of water A molecule is an aggregation of atomic nuclei and electrons that is sufficiently stable to possess
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of bonding which holds the atoms together in metal crystal. Valence electron: The electrons in the outer most energy level in an atom that takes part in chemical bonding are called valence electrons. Bonding electrons: The valence electrons actually involved in bond formation are called bonding electrons. Octet rule: In chemical bond formation‚ atoms interact- (i) by losing‚ (ii) by gaining or (iii) by sharing electrons to acquire a stable noble gas configuration. He
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Transition Metal: element of groups 3-12 * Energy level: a space with definite and fixed energy in which an electron is allowed to move * Orbit: circular/spherical path in which the electron can move around the nucleus * Electron Cloud: the region of an atom in which there is a probability that an electron exists * Quantum Mechanics: theory of the atom in which electrons are described in terms of their energies/probability patterns (model looks like smoke around a circle) * Principal
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Sample Paper – 2008 Class – Physics Class – XII Dual nature of matter Q.1. State the dependence of work function on kinetic energy of electrons emitted in a photocell. If the intensity of incident radiation is doubled‚ what changes occur in the stopping potential and photoelectric current? Q.2. How does the maximum kinetic energy of the emitted electrons vary with the work function? Q.3. the frequency of incident radiation is greater than the threshold frequency in a photocell. How will
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CARBON CARBON MULTIPLE BOND PRESENTED BY: WASIQUE AZHAR MSC CHEM (2 SEM) Some basic concept Electrophile : a species with a region of positive or partial positive charge electron-poor Nucleophile: a species with a region of negative or partial negative charge electron-rich TO LERN OBJECTIVE : Elecrophilic Addition to carbon-carbon double bond Stereochemistry of Elecrophilic addition reaction Hydrogenation of double and triple bond Nucleophilic Addition to carbon-carbon double
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Dense nucleus composed of neutrons (0 charge) and protons (+ charge) and surrounded by orbital electrons (- charge). Neutrons and protons firmly held in the nucleus while electrons are very loosely held and are easy to remove. When electrons are removed from the atom‚ two charged particles (ions) are produced the positively charged atom and the negative electron. Energy is absorbed to remove the electron from the atom. Atomic Notation Chemical symbols such as C for carbon‚ H for hydrogen‚ and
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400 BC Democritus: He hypothesized that all matter (plus space and time) is composed of tiny indestructible units‚ called atoms. Democritus performed no experiments. 1 .All matter consists of invisible particles called atoms. 2. Atoms are indestructible. 3. Atoms are solid but invisible. 4. Atoms are homogenous. 5. Atoms differ in size‚ shape‚ mass‚ position‚ and arrangement. ->Solids are made of small‚ pointy atoms. ->Liquids are made of large‚ round atoms. ->Oils are made of very fine
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THE VSEPR THEORY The VSEPR stands for ¡°Valence Shell Electron Pair Repulsion¡±‚ the theory is used for predicting the structure of molecules. The theory can be used in two main steps. First‚ the number of all bonding pairs and lone pairs is calculated‚ next‚ these pairs of electrons are rearranged in order to minimize the repulsion between them. Different number of bonding pairs and lone pairs of electrons can form different structure. When there are only two bonding pairs around the central
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subatomic particles that play the greatest role in cellular chemical reactions are electrons. protons. neutrons. isotopes. 0 out of 5 The correct answer is: electrons. Question 2 of 20 The structural unit that retains the properties of an element is the molecule. atom. cell. electron. 5 out of 5 Correct!! Question 3 of 20 Which of the following are found in the nucleus of an atom? Protons Neutrons Electrons A and B 0 out of 5 The correct answer is: A and B Question 4 of 20 The component
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Describe the difference between a mixture and a compound. A compound is a substance in which atoms of different elements are chemically held to one another. A mixture is a substance made by combining two or more different materials in such a way that no chemical reaction occurs. A mixture can usually be separated back into its original components‚ a compound cannot. Below are some examples of the differences between each. Compounds •Compounds are pure substances. •They are made up of two or more
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