diff --git a/opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py b/opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py
index 1fed32c0be..c470cb6969 100644
--- a/opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py
+++ b/opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py
@@ -63,6 +63,8 @@
 import typing
 from json import dumps
 from os import environ
+from types import ModuleType
+from typing import Dict, List, Optional, Union, cast
 from urllib import parse
 
 from opentelemetry.attributes import BoundedAttributes
@@ -75,10 +77,14 @@
 from opentelemetry.util._importlib_metadata import entry_points, version
 from opentelemetry.util.types import AttributeValue
 
+psutil: Optional[ModuleType] = None
+
 try:
-    import psutil
+    import psutil as pustil_module
+
+    pustil = pustil_module
 except ImportError:
-    psutil = None
+    pass
 
 LabelValue = AttributeValue
 Attributes = typing.Mapping[str, LabelValue]
@@ -147,6 +153,11 @@
 class Resource:
     """A Resource is an immutable representation of the entity producing telemetry as Attributes."""
 
+    _attributes: Dict[
+        str, Union[str, int, float, bool]
+    ]  # Example: Adjust according to actual expected types
+    _schema_url: str
+
     def __init__(
         self, attributes: Attributes, schema_url: typing.Optional[str] = None
     ):
@@ -173,7 +184,7 @@ def create(
         if not attributes:
             attributes = {}
 
-        resource_detectors = []
+        resource_detectors: List[ResourceDetector] = []
 
         resource = _DEFAULT_RESOURCE
 
@@ -182,6 +193,7 @@ def create(
         ).split(",")
 
         if "otel" not in otel_experimental_resource_detectors:
+
             otel_experimental_resource_detectors.append("otel")
 
         for resource_detector in otel_experimental_resource_detectors:
@@ -193,9 +205,8 @@ def create(
                             name=resource_detector.strip(),
                         )
                     )
-                ).load()()
+                )
             )
-
         resource = get_aggregated_resources(
             resource_detectors, _DEFAULT_RESOURCE
         ).merge(Resource(attributes, schema_url))
@@ -206,7 +217,7 @@ def create(
                 PROCESS_EXECUTABLE_NAME, None
             )
             if process_executable_name:
-                default_service_name += ":" + process_executable_name
+                default_service_name += ":" + str(process_executable_name)
             resource = resource.merge(
                 Resource({SERVICE_NAME: default_service_name}, schema_url)
             )
@@ -218,6 +229,8 @@ def get_empty() -> "Resource":
 
     @property
     def attributes(self) -> Attributes:
+        if self._attributes is None:
+            raise ValueError("Attributes are not set.")
         return self._attributes
 
     @property
@@ -241,7 +254,7 @@ def merge(self, other: "Resource") -> "Resource":
         Returns:
             The newly-created Resource.
         """
-        merged_attributes = self.attributes.copy()
+        merged_attributes = dict(self.attributes)
         merged_attributes.update(other.attributes)
 
         if self.schema_url == "":
@@ -257,7 +270,6 @@ def merge(self, other: "Resource") -> "Resource":
                 other.schema_url,
             )
             return self
-
         return Resource(merged_attributes, schema_url)
 
     def __eq__(self, other: object) -> bool:
@@ -268,15 +280,15 @@ def __eq__(self, other: object) -> bool:
             and self._schema_url == other._schema_url
         )
 
-    def __hash__(self):
-        return hash(
-            f"{dumps(self._attributes.copy(), sort_keys=True)}|{self._schema_url}"
-        )
+    def __hash__(self) -> int:
+        attributes_json = dumps(self._attributes.copy(), sort_keys=True)
+        return hash(f"{attributes_json}|{self._schema_url}")
 
-    def to_json(self, indent=4) -> str:
+    def to_json(self, indent: int = 4) -> str:
+        attributes = dict(self._attributes)
         return dumps(
             {
-                "attributes": dict(self._attributes),
+                "attributes": attributes,
                 "schema_url": self._schema_url,
             },
             indent=indent,
@@ -294,7 +306,7 @@ def to_json(self, indent=4) -> str:
 
 
 class ResourceDetector(abc.ABC):
-    def __init__(self, raise_on_error=False):
+    def __init__(self, raise_on_error: bool = False) -> None:
         self.raise_on_error = raise_on_error
 
     @abc.abstractmethod
@@ -343,7 +355,7 @@ def detect(self) -> "Resource":
                 ),
             )
         )
-        _process_pid = os.getpid()
+        _process_pid = str(os.getpid())
         _process_executable_name = sys.executable
         _process_executable_path = os.path.dirname(_process_executable_name)
         _process_command = sys.argv[0]
@@ -358,15 +370,16 @@ def detect(self) -> "Resource":
             PROCESS_EXECUTABLE_PATH: _process_executable_path,
             PROCESS_COMMAND: _process_command,
             PROCESS_COMMAND_LINE: _process_command_line,
-            PROCESS_COMMAND_ARGS: _process_command_args,
+            PROCESS_COMMAND_ARGS: "".join(_process_command_args),
         }
         if hasattr(os, "getppid"):
             # pypy3 does not have getppid()
-            resource_info[PROCESS_PARENT_PID] = os.getppid()
+            resource_info[PROCESS_PARENT_PID] = str(os.getppid())
 
         if psutil is not None:
             process = psutil.Process()
-            resource_info[PROCESS_OWNER] = process.username()
+            username = cast(str, process.username())
+            resource_info[PROCESS_OWNER] = username
 
         return Resource(resource_info)
 
@@ -374,7 +387,7 @@ def detect(self) -> "Resource":
 def get_aggregated_resources(
     detectors: typing.List["ResourceDetector"],
     initial_resource: typing.Optional[Resource] = None,
-    timeout=5,
+    timeout: int = 5,
 ) -> "Resource":
     """Retrieves resources from detectors in the order that they were passed
 
diff --git a/tox.ini b/tox.ini
index dfa3edd028..8f6e1079f8 100644
--- a/tox.ini
+++ b/tox.ini
@@ -332,6 +332,7 @@ commands =
   coverage: {toxinidir}/scripts/coverage.sh
 
   mypy: mypy --install-types --non-interactive --namespace-packages --explicit-package-bases opentelemetry-api/src/opentelemetry/
+  mypy: mypy --install-types --non-interactive --namespace-packages --explicit-package-bases opentelemetry-sdk/src/opentelemetry/sdk/resources
   mypy: mypy --install-types --non-interactive --namespace-packages --explicit-package-bases opentelemetry-semantic-conventions/src/opentelemetry/semconv/
 
 ; For test code, we don't want to enforce the full mypy strictness