Answer:
Least precise recorded time is 48.9 seconds.
Explanation:
Here, we need to write the recorded time that is least precise. The given options are (a) 48.9107 s (b) 48.91 s (c) 48.910 s (d) 48.9 s. The precision in any measurement is defined as closeness in any measurement.
First option is most precise as it is precised to four decimal places. Second option is precised to two decimal places. Third option is precised to 3 decimal places. But in option fourth, the recorded time is precised to one decimal place.
Hence, the correct option is (d).
B. The atom has 7 protons and 7 electrons.
C. The atom has 19 electrons and 19 neutrons.
D. The atom has 15 neutrons and 15 electrons.
Answer:
The correct answer is the Mesosphere. Mesosphere is the layer of the Earth's atmosphere that is directly above the stratopause and directly below the mesopause.
Explanation:
Answer: An atom valence electron shell determines its chemical reactivity.
Explanation:
An atom's valence electron shell determines its chemical reactivity. The amount of electrons in the outermost shell of an atom is its valence electron and it determines how reactive the atom is.
The reactivity of an atom depends on the number of electrons in its outermost shell. Atoms that has their outermost electrons full e.g noble gases like argon, krypton etc are unreactive because there is no room for the atom to donate or accept any electron.
Elements like sodium and chlorine are reactive because they possesses 1 and 7 electrons in their outermost shell respectively as such they can donate and accept electrons making them reactive elements.
The valence electron shell of an atom determines its chemical reactivity. This is due to the role these outermost electrons play in the formation of chemical bonds. Atoms aim to achieve a stable state, typically with eight electrons in their outermost shell, through accepting, donating, or sharing electrons.
The correct answer to the multiple choice question about the atom's valence electron shell is '2. determines its chemical reactivity'. The outermost shell of an atom is known as the valence shell. This shell, holding the valence electrons, is essential in determining an atom's chemical reactivity. This is because it's the valence electrons that are engaged in the formation of chemical bonds.
Chemical reactivity refers to the ease with which an atom gains, loses, or shares electrons. Stable atoms, like helium or larger atoms with eight electrons, are less likely to participate in chemical reactions. They already have a filled valence shell. However, other atoms, those with less than eight electrons, will strive to complete their outer shell by interacting with other atoms, either accepting, donating or sharing electrons to achieve stability.
Importantly, not all elements have enough electrons to completely fill their outermost shells and so they form chemical bonds by sharing, accepting, or donating electrons to other atoms. The formation of these bonds is largely determined by what is often referred to as the 'octet rule', which states that atoms seek to fill or have eight electrons in their outermost electron shell to achieve greater stability.
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