Answer:
John Dalton
Explanation:
John Dalton in 1808 suggested that all matter consists of tiny particles called atoms and that the atoms of a specific element are identical.
He postulated the Dalton's atomic theory which has the following important parts;
- All matters consists of indivisible particles called atoms
- Atoms of the same element are similar and are different from atoms of other elements.
- Atoms can neither be created nor destroyed.
- Atoms combine in simple whole ratios to form compounds.
Answer:
The correct row is B.
Explanation:
The formation of the magnesium ion, Mg²⁺, comes from the removal of 2 electrons from the valence shell of the magnesium atom.<em> </em>Since the remotion is of electrons, the nucleus of the atom remains the same, so the number of protons and the number of neutrons does not change.<em> </em>
If the number of proton change, then the atom also change, since the identity of an atom is related to the atomic number which is the same to the proton number.
Now, if the number of neutrons changes, then we would be in the presence of an isotope of the magnesium atom.
Therefore, the correct row is B.
I hope it helps you!
Answer:
(i) Bohr; (ii) de Broglie; (iii) Heisenberg (v) Schrödinger
Explanation:
(i) Niels Bohr — 1913 — proposed that electrons travel in fixed orbits with <em>quantized energy levels</em> and that they jump from one energy level to another by absorbing or emitting quanta of light.
(ii) <em>Louis de Broglie</em> — 1924 — proposed the wave nature of electrons and suggested that all matter behaves as both waves and particles (<em>wave-particle duality</em>).
(iii) Werner Heisenberg — 1927 — formulated quantum mechanics in terms of matrices and proposed his famous <em>uncertainty principle</em>.
(v) Erwin Schrödinger — 1926 — applied wave mechanics to the electron in a hydrogen atom, showing that electrons exist in <em>orbitals </em>rather that orbits.
(iv) <em>Ernest Rutherford</em> — 1911 — proposed that atoms have most of their mass in a central nucleus (<em>nuclear atom</em>). Quantum mechanics had not yet been invented.
Substances that have a define size and shape and vibrating particles that are close together are called Solid.
Explanation:
There are three states of matter - solid, liquid and gas.
Lets talk about solid state in detail.
In solid particles are closely packed and so they have very less or no space to move which results in vibrating particles. This results in solid substances having a fixed shape and volume.
The particles have very little space in between them, so it is not easy to compress solid.
There is no free space for particles to slide over each other, which does not allow solids to flow.
Also, particles in solid have a regular arrangement, they are not randomly packed.
0.0788 will be the number of moles of silver in coin.
<h3><u>How to find the number of moles?</u></h3>
A mole is the mass of a material made up of the same number of fundamental components. Atoms in a 12 gram example are identical to 12C. Depending on the material, the fundamental units may be molecules, atoms, or formula units.
A mole fraction shows how many chemical elements are present. The value of 6.023 x 10²³ is equivalent to one mole of any material (Avagadro's number). It can be used to quantify the chemical reaction's byproducts. The symbol for the unit is mol.
The number of moles formula is denoted by the following expression:
Number of moles = Mass of substance/mass of one mole
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