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  2. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    If an atom has more electrons than protons, then it has an overall negative charge and is called a negative ion (or anion). Conversely, if it has more protons than electrons, it has a positive charge and is called a positive ion (or cation). The electrons of an atom are attracted to the protons in an atomic nucleus by the electromagnetic force.

  3. Periodic trends - Wikipedia

    en.wikipedia.org/wiki/Periodic_trends

    The ionization energy is the minimum amount of energy that an electron in a gaseous atom or ion has to absorb to come out of the influence of the attracting force of the nucleus. It is also referred to as ionization potential. The first ionization energy is the amount of energy that is required to remove the first electron from a neutral atom.

  4. History of atomic theory - Wikipedia

    en.wikipedia.org/wiki/History_of_atomic_theory

    The current theoretical model of the atom involves a dense nucleus surrounded by a probabilistic "cloud" of electrons. Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years in response to scientific discoveries.

  5. Atomic physics - Wikipedia

    en.wikipedia.org/wiki/Atomic_physics

    The atom is said to have undergone the process of ionization. If the electron absorbs a quantity of energy less than the binding energy, it will be transferred to an excited state. After a certain time, the electron in an excited state will "jump" (undergo a transition) to a lower state.

  6. Board examination - Wikipedia

    en.wikipedia.org/wiki/Board_examination

    The 2025 CBSE board examination for Class 10 were held from 15 February till 18 March and from 15 February till 4 April for class 12. The usual starting time for each exam was 10:30 am( IST ) but depending on the length and/or maximum marks for the subject, the finishing time was either 12:30 pm ( IST ) (2 hours, shorter exams, usually 40-50 ...

  7. Secondary School Certificate - Wikipedia

    en.wikipedia.org/wiki/Secondary_School_Certificate

    The SSC or SSLC is obtained on passing the “Class 10th Public Examination” which is commonly referred to as “Class 10th Board Examinations” in India. The SSC is also known as Matriculation in many states of India. [6] The SSC exam is considered one of the most important exams in India. The percentage of your SSC exams determine which ...

  8. Atomicity (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Atomicity_(chemistry)

    Atomicity is the total number of atoms present in a molecule of an element. For example, each molecule of oxygen (O 2) is composed of two oxygen atoms.Therefore, the atomicity of oxygen is 2.

  9. Block (periodic table) - Wikipedia

    en.wikipedia.org/wiki/Block_(periodic_table)

    Chemistry: Facts, patterns, and principles, Addison-Wesley, London, pp. 487−489 The d-block, with the d standing for "diffuse" and azimuthal quantum number 2, is in the middle of the periodic table and encompasses elements from groups 3 to 12; it starts in the 4th period .