Question

Which statements are consistent with Dalton's atomic theory as it was originally stated? Explain your answers. (a) Calcium and titanium atoms have the same mass. (b) Neon and argon atoms are the same. (c) All cobalt atoms are identical. (d) Sodium and chlorine atoms combine in a \(1: 1\) ratio to form sodium chloride.

Short answer

Statements (c) 'All cobalt atoms are identical' and (d) 'Sodium and chlorine atoms combine in a 1:1 ratio to form sodium chloride' are consistent with Dalton's atomic theory. Statements (a) and (b) are not consistent with the theory.

Step-by-step solution

Review of Dalton's Atomic Theory

Before addressing the statements, recall the main points of Dalton's atomic theory: 1) Elements are composed of extremely small particles called atoms. 2) All atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from those of all other elements. 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms.

Assessing Statement (a)

Statement (a) says that calcium and titanium atoms have the same mass. According to Dalton's atomic theory, atoms of different elements would have different masses. Therefore, this statement is not consistent with Dalton's atomic theory.

Assessing Statement (b)

Statement (b) claims that neon and argon atoms are the same. Dalton's theory states that atoms of different elements have different properties; since neon and argon are different elements, their atoms would be different. Thus, this statement is not consistent with Dalton's atomic theory.

Assessing Statement (c)

Statement (c) asserts that all cobalt atoms are identical. This is consistent with Dalton's theory, which states that atoms of a given element are identical in size, mass, and chemical properties. Thus, this statement is consistent with Dalton's atomic theory.

Assessing Statement (d)

Statement (d) says that sodium and chlorine atoms combine in a 1:1 ratio to form sodium chloride. Dalton's theory posits that compounds are formed by a combination of atoms of different elements in simple whole-number ratios. This statement aligns with the theory as it describes a 1:1 ratio, a simple whole number. Therefore, this statement is consistent with Dalton's atomic theory.

Key concepts

Atomic Mass

The concept of atomic mass is pivotal in understanding the backbone of Dalton's atomic theory, which posits that atoms of different elements have distinct masses. In simpler terms, atomic mass can be thought of as the 'weight' of an atom, albeit on an incredibly tiny scale. It's measured in atomic mass units (amu), where one amu is defined as one-twelfth the mass of a carbon-12 atom.

To put this into context with the given exercise statement (a), calcium and titanium, being different elements, would indeed possess unique atomic masses. Thus, asserting they have the same mass contradicts Dalton's theory. It's vital for students to grasp that recognizing each element's unique atomic mass is key to understanding the formation of compounds and predict the outcomes of chemical reactions.

Chemical Reaction

A chemical reaction can be described as a dance of atoms, where they rearrange themselves to form new substances. Dalton's atomic theory interprets a chemical reaction not as a creation or destruction of atoms but rather their reorganization. This concept is foundational to how we predict which substances will be formed and in what proportion.

In educational terms, imagine each atom as a type of building block; during a chemical reaction, these blocks are taken apart and reassembled into new structures. For instance, statement (d) from the exercise highlights that sodium and chlorine atoms combine in a 1:1 ratio to create sodium chloride. This exemplifies the atomic theory concept that compounds are formed from atoms of different elements coming together in fixed, simple numeric ratios.

Atomic Theory Consistency

Determining whether ideas or observations are consistent with Dalton's atomic theory is a crucial skill in evaluating scientific theories. The core of Dalton's theory holds that elements are made of atoms that are identical in mass and properties for a given element, and different for different elements.

From our exercise, statement (c) aligns perfectly with this theory, as it implies that all atoms of cobalt, being the same element, are identical. In contrast, statement (a) is inconsistent with Dalton’s theory since it suggests that two different elements, calcium and titanium, share the same atomic mass, which Dalton's principles reject. For students to successfully apply Dalton's theory to various chemical problems, they need to internalize the distinction between consistency and discrepancy when it comes to atomic theory.

Chemical Compounds

Under the Daltonian view, chemical compounds are pure substances that form when atoms of two or more different elements link together in specific proportions. Hence, a compound embodies a fixed ratio that reflects the numbers and types of atoms connecting to create a new substance.

To envision this, think of chemical compounds like recipes—the ingredients (atoms) must be combined in precisely the right amounts. Returning to statement (d), the creation of sodium chloride demonstrates this concept, as the 1:1 ratio mirrors Dalton’s theory that compounds result from a particular combination of atoms. It’s essential for students to appreciate the fixed nature of these atomic 'recipes' to understand why compounds have consistent properties and compositions.