The nucleus of an atom contains the majority of its mass and is composed of two types of subatomic particles: protons and neutrons.
1. Protons: Protons are positively charged particles found in the nucleus of an atom. Each proton carries a charge of +1 and has a relatively high mass compared to electrons. The number of protons in an atom's nucleus determines its atomic number, which in turn defines the element. In the case of helium-4 (He-4), it has an atomic number of 2, indicating that there are two protons in its nucleus.
2. Neutrons: Neutrons are electrically neutral particles, meaning they have no net charge. They are also located in the nucleus of an atom. Neutrons contribute to the mass of the nucleus and help stabilize it by balancing the electrostatic repulsion between positively charged protons. Helium-4, being a stable isotope of helium, has two neutrons in its nucleus, along with the two protons.
Electrons, on the other hand, are found in electron shells or orbitals outside the nucleus, not within it. Their role is to move around the nucleus and create the electron cloud or electron configuration, which determines an atom's chemical properties.
In summary, the nucleus of a helium-4 atom consists of neutrons and protons, making option (3) "neutrons and protons" the correct choice. Electrons, which are negatively charged, are located outside the nucleus and are involved in chemical interactions and bonding.
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Explanation:
Given parameters:
Mass of sample X = 15.5g
Mass of sample Y = 42.5g
Unknown:
Mass of reactant and product = ?
Solution:
We can solve this problem by applying the law of conservation of mass. The law states that "in a chemical reaction, matter is neither created nor destroyed but changed from one form to another".
We expect that the sum of the mass of the reactant will be equal to that of the product;
Mass of reactant = mass of X + mass of Y = 15.5g + 42.5g = 58g
So, mass of XY₃ = 58g
B. 6
C. 2
D. 10
Answer : The correct option is, (A) 8
Explanation :
Octet rule : It is the tendency of atoms to have eight electrons in the valence shell. When the atoms have fewer than eight electrons then they tend to react and form the more stable compounds.
Or we can say that the atoms attempt to get a noble gas electron configuration, which is eight valence electrons.
For example : As we know that the sodium has one valence electron, so if giving it up then the result in the same electron configuration as the neon and chlorine has seven valence electrons, so if it takes one it will have eight and the result in the same electronic configuration as the argon.
Hence, the correct option is, (A) 8
The type of stoichiometric calculation that does not require the use of the molar mass is a calculation involving molar or stoichiometric ratios which are derived directly from the coefficients in a balanced chemical equation.
In stoichiometry, there are several types of calculations that can be performed. However, the type of stoichiometric calculation that does not require the use of the molar mass is the calculation involving the molar ratio, or stoichiometric ratio. This refers to the ratio of coefficients in a balanced chemical equation, which we use to determine the relative amounts of each substance involved in a chemical reaction.
An example of this is a balanced equation for the formation of water: H2 + 0.5O2 -> H2O. In this equation, the molar or stoichiometric ratio of hydrogen (H2) to oxygen (O2) to water (H2O) is 2:1:2. If we are given the number of moles of one substance, we can use this molar ratio to find the number of moles of any other substance in the equation, without needing to know their molar masses. This constitutes a stoichiometric calculation without the need for molar mass.
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(b) Solid chromium(III) hydroxide reacts with nitrous acid.
(c) Aqueous nitric acid and aqueous ammonia react.
The mass percent of hydrogen in diethyl ether is 1.36%.
To calculate the mass percent of hydrogen in diethyl ether, we need to determine the mass of hydrogen in the compound and divide it by the total mass of diethyl ether. The formula of diethyl ether is C4H10O, so the molar mass is 74.12 g/mol. The molar mass of hydrogen is 1.008 g/mol.
Mass percent of hydrogen = (mass of hydrogen / mass of diethyl ether) × 100%
Mass percent of hydrogen = (1.008 g/mol / 74.12 g/mol) × 100% = 1.36%
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The molecules AlCl3, CCl4, SCl2, and S3 have different geometries and bond angles due to the number of electron bonding pairs. As such, by increasing bond angles, the order is SCl2 < CCl4 < AlCl3 < S3.
The question asks us to sort the molecules AlCl3, CCl4, SCl2, and S3 by increasing bond angles about the central atom. To do this, we need to examine the geometry and the bond angles produced by the electronic arrangements of each molecule.
In AlCl3, the central atom, Al, has three bonded pairs of electrons resulting in a trigonal planar structure with bond angles of 120°. In CCl4, carbon is the central atom, and it forms four bonds with chlorine atoms, creating a tetrahedral structure. The bond angle for this molecule is approximately 109.5°. For SCl2, sulfur forms two bonds and has two lone pairs of electrons. The VSEPR model predicts a bent or V shape for the molecule, resulting in bond angles less than 109.5°. Lastly, S3 is a non-polar molecule with bond angles of 120°.
Therefore, the correct order of increasing bond angles would be SCl2 < CCl4 < AlCl3 < S3.
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